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https://doi.org/10.1177/1071100717718131
Foot & Ankle International®
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DOI: 10.1177/1071100717718131
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Article
Introduction
Achilles tendon tears are one of the most common foot and
ankle injuries in both contact and noncontact sports.10 These
injuries are a source of significant morbidity with an inci-
dence as high as 18 per 100 000 people.15-17,20 Recent evi-
dence suggests that the incidence is increasing secondary to
an increase in athletic participation that accounts for 68% of
all Achilles tendon tears.21,22
The pathophysiology of Achilles tendon tears involves the
interplay of intrinsic (degenerative changes, hypovascularity,
repetitive microtrauma) and extrinsic (rapid acceleration/
deceleration) factors.22 Elite level athletes required to per-
form explosive changes in direction and extreme loading of
the Achilles tendon are at increased risk for Achilles tendon
tears.17 This explosive acceleration and rapid deceleration
associated with Achilles tendon tears is displayed and often
required by National Football League (NFL) players.
Many elite athletes elect for operative repair of their torn
Achilles tendon secondary to lower rerupture rates,
improved strength, and high return to sport.7 However,
recent studies demonstrated that injuries that are severe
718131FAIXXX10.1177/1071100717718131Foot & Ankle InternationalJack et al
research-article2017
1Houston Methodist Orthopedics and Sports Medicine, Houston, TX,
USA
Corresponding Author:
Joshua Harris, MD, Houston Methodist Orthopedics and Sports
Medicine, 6445 Main Street, Suite 2500, Houston, TX 77030, USA.
Email: Joshuaharrismd@gmail.com
Performance and Return to Sport After
Achilles Tendon Repair in National
Football League Players
Robert A. Jack II, MD1, Kyle R. Sochacki, MD1, Stephanie S. Gardner, MD1,
Patrick C. McCulloch, MD1, David M. Lintner, MD1, Pedro E. Cosculluela, MD1,
Kevin E. Varner, MD1, and Joshua D. Harris, MD1
Abstract
Background: Achilles tendon injuries are common in sports, including football. The purpose of this study was to determine
(1) return-to-sport rate in National Football League (NFL) players following Achilles tendon repair, (2) postoperative career
length and games per season, (3) pre- and postoperative performance, and (4) postoperative performance compared with
control players matched by position, age, years of experience, and performance.
Methods: Publicly available records were used to identify NFL players who underwent Achilles tendon repair and matched
controls were identified. Ninety-five players (98 surgeries) were analyzed (mean age 28.2 ± 2.8 years; mean 5.5 ± 2 .8 years
in NFL at time of surgery). Demographic and performance data were collected. Comparisons between case and control
groups and preoperative and postoperative time points were made using paired-samples Student t tests.
Results: Seventy-one (72.4%) players were able to return to sport in the NFL at a mean of 339.8 ± 84.8 days following
surgery. Thirty-one (32%) Achilles tendon repairs were performed during training camp or preseason. Controls (3.6 ± 2.1
years) had a significantly longer NFL career (P < .05) than players who underwent Achilles tendon repair (2.7 ± 2.1 years).
There was no significant difference in games per season in subsequent seasons following surgery compared with controls.
Postoperative performance scores were significantly worse (P < .05) for running backs (RBs) (n = 4) and linebackers (LBs)
(n = 12) compared to preoperative scores. LBs had significantly worse postoperative performance scores when compared
to matched controls (P < .05).
Conclusion: Following Achilles tendon repair, less than 75% of players returned to the NFL. Postoperative career length
was 1 season shorter than matched controls. No difference was observed in the number of games per season played
compared to matched controls. Postoperative performance scores were significantly worse for RBs and LBs compared to
preoperative and LBs had significantly worse postoperative performance when compared to matched controls.
Level of Evidence: Level III, retrospective comparative series.
Keywords: Achilles tendon, NFL, football, surgery, return to sport
2 Foot & Ankle International 00(0)
enough to warrant operative intervention in NFL players
can have a negative effect on postoperative performance,
return to sport (RTS), and length of career.4,18 Given the
increasing revenue and popularity of the NFL, it is impor-
tant to understand operative outcomes in this patient popu-
lation. To our knowledge, there have been no published
studies to date that have compared postoperative perfor-
mance statistics with matched controls following Achilles
tendon repair in NFL athletes.
The purpose of this study was to determine (1) RTS rate
in NFL players following Achilles tendon repair, (2) post-
operative career length and games per season, (3) pre- and
postoperative performance, and (4) postoperative perfor-
mance compared with control players matched by position,
age, years of experience, and performance. The authors
hypothesized that NFL players who underwent Achilles
tendon repair would have (1) a 75% RTS rate, (2) a postop-
erative career length and games per season significantly
less than that of matched controls, (3) significantly worse
postoperative performance compared to preoperative, and
(4) significantly worse performance postoperatively when
compared with matched controls.
Methods
Players in the NFL who sustained an Achilles tendon tear
and underwent repair were evaluated (Figure 1). These play-
ers were identified through NFL team websites, publicly
available Internet-based injury reports, player profiles and
biographies, and press releases. The search was manually
conducted by 2 orthopedic surgery residents with validation
of the findings by the senior author. Searches were per-
formed for all NFL teams and players.
All players identified who met inclusion criteria were
evaluated in this study as it related to RTS rate. A player
was deemed to have RTS if he played in any NFL game
Figure 1. Flowchart illustrating application of exclusion criteria.
Jack et al 3
after surgery. A player did not RTS if he did not play in any
NFL game after surgery. Inclusion criteria were any NFL
athletes on an active roster or listed on injured reserve in the
NFL prior to Achilles tendon tear. Players were included if
they were found to have Achilles tendon repair surgery as
reported by at least 2 separate sources. Athletes who were
injured and underwent procedures before completing their
first NFL regular season were excluded. Players who sus-
tained an Achilles tendon tear and underwent Achilles ten-
don repair in the 2015-2016 season were excluded from
analysis because they had less than a 1-year opportunity to
return to sport. In addition, online reports that were conflict-
ing, incomplete, or did not have a date of surgery were also
excluded from the study. Ninety-eight surgeries in 95 play-
ers were analyzed (Table 1).
Demographic variables including a player’s age, posi-
tion, prior professional experience, and date of surgery
were recorded. Players were categorized by their posi-
tions, including quarterback “QB,” running back “RB,”
tight end “TE,” wide receiver “WR,” offensive lineman
“OL,” defensive lineman “DL,” linebacker “LB,” defen-
sive back “DB,” kicker “K,” or punter “P.” Performance
statistics were collected from profootballreference.com
for each player identified before and after Achilles tendon
repair (Appendix A). Statistics were collected for regular
season NFL games only, with preseason and playoff
games excluded.
A control group was selected to compare data. Controls
were matched to study cases based on position, age, years
of experience, and performance data prior to the surgery
date (Table 2). Each control was given an index date that
matched the case player’s surgery date to compare postop-
erative or postindex performance. For example, if a player
had Achilles repair surgery 3 years into his career, the con-
trol’s index date was 3 years into his career.
Player statistics for cases pre- and postoperative and
controls pre- and postindex were collected and aggregated.
Each statistical category was divided by games played to
account for discrepancies in number of games played per
season. A player’s performance score (Appendix B) was
then calculated by using a previously published and stan-
dardized scoring system based on metrics important to the
player’s specific position.5,18,25 Statistics per game were
used to calculate each performance score per game.
All players were included in RTS, games per season,
and career length analysis. A Kaplan-Meier survivorship
curve with ‘‘retirement’’ as the endpoint was constructed
postoperatively for cases and postindex for controls.
Positions without previously defined performance scores
(punters, kickers, and offensive lineman) were excluded
from performance score analysis. Comparisons between
case and control groups and preoperative and postopera-
tive time points were made using paired-samples Student
t tests (http://in-silico.net/tools/statistics/ttest) using P
less than .05.
Results
One player retore his ipsilateral Achilles tendon within 1
month of surgery and returned to sport. He was counted as
a single event. One player retore his ipsilateral Achilles and
did not return to sport. He was counted as a single event.
One player tore both Achilles 2 years apart and was counted
as 2 separate events. Seventy-one (72.4%) players were
able to return to sport in the NFL. The overall 1-year sur-
vival rate of players undergoing Achilles tendon repair sur-
gery was 67.7% (Figure 2). Players in the control group (3.6
± 2.1 years) were in the NFL significantly longer (P < .001)
than players who underwent Achilles tendon repair surgery
(2.7 ± 2.1 years) (Table 3). Players in the control group
(12.9 ± 2.8 games per season) played in a similar number of
games per season postindex than players who underwent
Table 1. Number of Surgeries With Return to Sport (RTS)
Data by Position.
Position n RTS, n RTS, % Days to RTS
QB 5 5 100.0 326.4 ± 17.5
RB 11 5 45.5 363.6 ± 119.3
TE 5 3 60.0 326.3 ± 74.1
WR 10 8 80.0 317.5 ± 160.4
DB 12 9 75.0 336.2 ± 38.5
LB 19 14 73.7 351.1 ± 42.7
DL 21 17 80.1 328.2 ± 83.4
OL 13 8 61.5 341.9 ± 98.1
K 1 1 100.0 501
P 1 1 100.0 403
Total 98 71 72.4 339.8 ± 84.8
Abbreviations: DB, defensive back; DL, defensive lineman; K, kicker;
LB, linebacker; OL, offensive lineman; P, punter; QB, quarterback; RB,
running back; RTS, return to sport; TE, tight end; WR, wide receiver.
Figure 2. Kaplan-Meier survival analysis for cases and controls.
Zero (0) signifies year of surgery for cases and index year for
controls.
4 Foot & Ankle International 00(0)
Achilles tendon repair surgery (12.6 ± 3.4) postsurgery
(Table 3).
Thirty-two (100%) of the NFL’s teams had at least 1
Achilles tendon repair surgery performed. The team with
the greatest number of players undergoing Achilles tendon
repair was the New York Jets, with 9 (9%) players. The
most common position to undergo Achilles tendon repair
surgery was DL, with 21 (21%) players (Table 1). Sixty-
three (64%) Achilles tendon repairs occurred in the
off-season.
There were no significant (P > .05) differences in demo-
graphic, performance, and games per season data between
cases and matched controls presurgery and preindex
(Tables 2-4). Postoperative performance scores were signifi-
cantly worse for RBs (P = .04) and LBs (P = .03) compared
to preoperative scores (Figure 3). There was a statistically
significant (P = .04) decrease in games per season for DL
cases following surgery (Table 4). LBs had significantly
worse postoperative performance scores when compared to
postindex matched controls (P < .05) (Figure 3). There was
a clinically significant decline in performance statistics fol-
lowing Achilles tendon repair compared to controls for QBs
(5 touchdowns and 60 passing yards per year), RBs (5 touch-
downs per year), TEs (6 touchdowns per year), DBs (2 inter-
ceptions and 1 pass defended per year), and LBs (7 sacks or
28 tackles per year).
Discussion
The authors hypothesized that NFL players who underwent
Achilles tendon repair would have (1) a 75% RTS rate, (2) a
postoperative career length and games per season signifi-
cantly less than that of matched controls, (3) significantly
worse postoperative performance compared to preoperative,
Table 3. Games per Season and Career Length Postsurgery and Postindex for Cases and Controls.
Games per Season, n (Mean ± SD) Career Length, y (Mean ± SD)
Position n Cases Controls P Value Cases Controls P Value
QB 5 10.0 ± 3.2 9.6 ± 4.4 .886 6.2 ± 3.5 5.6 ± 4.1 .671
RB 5 13.0 ± 2.7 12.6 ± 1.6 .808 1.3 ± 0.8 3.2 ± 1.8 .084
TE 3 13.1 ± 3.0 8.4 ± 1.3 .198 2.3 ± 1.5 2.2 ± 1.7 .844
WR 8 10.9 ± 5.4 14.8 ± 1.1 .101 2.7 ± 2.4 4.1 ± 2.0 .195
DB 9 12.7 ± 2.2 13.3 ± 2.3 .361 2.4 ± 1.2 3.9 ± 1.5 .022*
LB 14 14.2 ± 2.4 13.7 ± 2.4 .606 2.5 ± 2.2 3.7 ± 2.2 .001*
DL 17 12.2 ± 4.0 13.4 ± 2.5 .343 2.4 ± 1.6 3.3 ± 2.0 .002*
OL 7 12.8 ± 2.5 12.3 ± 2.5 .775 3.4 ± 1.0 3.1 ± 1.1 .209
K 1 13.0 8.0 1.3 2.0
P 1 16.0 16.0 1.0 4.0
Overall 70 12.6 ± 3.4 12.9 ± 2.8 .513 2.7 ± 2.1 3.6 ± 2.1 <.001*
Abbreviations: DB, defensive back; DL, defensive lineman; K, kicker; LB, linebacker; OL, offensive lineman; P, punter; QB, quarterback; RB, running
back; SD, standard deviation; TE, tight end; WR, wide receiver.
*Statistically significant.
Table 2. Age and Experience for Each Position at Time of Surgery (for Cases) and Index Time (for Controls).
Age, y (Mean ± SD) Experience (Mean ± SD)
Position n Cases Controls P Value Cases Controls P Value
QB 5 30.8 ± 3.7 31.1 ± 4.2 .531 8.1 ± 3.8 7.7 ± 5.0 .587
RB 5 27.9 ± 3.5 27.4 ± 2.9 .352 4.4 ± 2.7 4.4 ± 3.1 1.000
TE 3 28.5 ± 3.4 28.4 ± 3.9 .792 6.1 ± 3.6 6.1 ± 3.6 1.000
WR 8 25.9 ± 2.5 25.8 ± 2.5 .876 3.1 ± 2.4 3.0 ± 2.4 .351
DB 9 27.3 ± 2.1 27.5 ± 2.3 .399 4.9 ± 2.5 4.8 ± 2.2 .347
LB 14 28.1 ± 2.1 27.9 ± 2.4 .607 5.8 ± 2.1 5.8 ± 2.1 1.000
DL 17 28.5 ± 3.2 28.2 ± 3.4 .317 5.6 ± 3.2 5.6 ± 3.1 .332
OL 7 29.4 ± 1.7 29.4 ± 2.3 .957 6.3 ± 2.0 6.3 ± 2.0 1.000
K 1 27.3 27.2 5.2 5.2
P 1 29.5 29.1 6.3 6.3
Overall 70 28.2 ± 2.8 28.0 ± 3.0 .309 5.5 ± 2.8 5.4 ± 2.9 .199
Abbreviations: DB, defensive back; DL, defensive lineman; K, kicker; LB, linebacker; OL, offensive lineman; P, punter; QB, quarterback; RB, running
back; SD, standard deviation; TE, tight end; WR, wide receiver.
Jack et al 5
and (4) significantly worse performance postoperatively
when compared with matched controls. The first study
hypothesis was confirmed because there was a 72.4% RTS
rate. The remaining hypotheses were partially confirmed in
that the postoperative career length was significantly less
than matched controls, postoperative games per season was
not significantly different, RBs and LBs had significantly
worse postoperative performance, and LBs had significantly
worse postoperative performance when compared to matched
controls.
One previous study investigated RTS and postoperative
performance for players who underwent Achilles tendon
repair in the NFL.18 The prior study demonstrated an RTS of
72.5% in 80 NFL athletes.18 The RTS from this prior study is
nearly identical to the results of the present study with an
RTS of 72.4% in 95 NFL athletes. However, this study did
not evaluate performance scores for specific position groups
and did not compare the outcomes of Achilles tendon repair
against matched controls. By using controls that were age-,
NFL experience-, and performance-matched, the current
study was able to improve performance data comparisons
for case players against controls at the same point in their
career. By simply comparing a player to himself, rapid
improvements (or regressions) in performance that are prev-
alent among similar players in the league may otherwise not
be accounted for. Furthermore, there may be the same
pathology present on the contralateral side similar to that of
the operative side, with recent studies demonstrating a con-
tralateral Achilles tendon rupture rate as high as 6.4%.11,21,26
Despite an RTS of 72.4%, there was a large number of
players who retire within the next few seasons after surgery
and index year. By year 3 postsurgery, only 28.1% of play-
ers who underwent Achilles tendon repair surgery remained
in the NFL. The average career length in the NFL is reported
as 6 years for players making an opening day roster in their
rookie season and 3.3 years for all NFL players overall.24
The average experience for players in this investigation was
5.5 years, already surpassing the overall career length aver-
age. The average career length after Achilles tendon repair
surgery has previously been described as 1.6 years.18 The
current investigation found an average career length of 2.7
years after Achilles tendon repair surgery. The increase in
career length in this investigation is likely due to more
recent seasons included in the current study (an additional 2
NFL seasons). The current investigation also found a sig-
nificant difference in career length after surgery when com-
paring cases (2.7 years) to controls (3.6 years), which has
not previously been described.
The highest number of Achilles tendon repair surgeries
occurred in DL (21), LB (19), and OL (13). This is a similar
distribution to a previous study looking at the effect of
injury on a career in the NFL in which DL and OL had the
highest and third highest incidence of injury, respectively.4
Interestingly, offensive (37.1 ± 1.9) and defensive (34.6 ±
1.4) linemen have the highest body mass index (BMI) in
NFL players.14 With recent studies demonstrating a signifi-
cantly increased incidence of Achilles tendon pathology in
patients with elevated BMI, the increased number of
Achilles tendon injuries in these players could be secondary
to the elevated BMI.12,13,23
Prior studies have also failed to comment on perfor-
mance and RTS differences between position groups fol-
lowing Achilles tendon repair. The RBs’ and LBs’
performance significantly regressed postoperatively, and
the LBs had significantly worse performance postopera-
tively compared to matched controls. There was an average
performance score difference per game of 1.9 for RBs and
1.8 for LBs. Extrapolated over a 16-game season, this
results in a performance score difference of 30.4 and 28.8
for RBs and LBs, respectively. Using the performance
score, RBs had 5 fewer touchdowns and LBs had 7 fewer
sacks and 28 fewer tackles compared to matched controls,
indicating both clinically and statistically significant results.
Furthermore, the TE and DB positions regressed postop-
eratively while their controls remained similar or improved.
There is an average performance score difference per game
of 2.3 and 0.7 for TEs and DBs, respectively. Extrapolated
over a 16-game season, the result is a performance score
difference of 36.8 for TEs and 11.2 for DBs, which equates
to 6 touchdowns per season for TEs and 2 interceptions and
1 pass defended per season for DBs. The QBs’ performance
scores decreased postoperatively and postindex in the con-
trols resulting in a performance score difference per game
of 1.4 between the cases and controls. Using the same logic,
this results in 5 touchdowns and 60 passing yards per
Table 4. Mean Games per Season for Cases and Controls
Presurgery and Preindex as well as Cases Postsurgery.
Presurgery and
Preindex
(Mean ± SD)
Postsurgery
(Mean ± SD)
Position Cases Controls P ValueaCases P Valueb
QB 10.9 ± 4.4 10.4 ± 3.3 .494 10.0 ± 3.2 .715
RB 12.9 ± 4.7 12.9 ± 2.8 .999 13.0 ± 2.7 .982
TE 13.9 ± 1.4 14.4 ± 1.8 .725 13.1 ± 3.0 .667
WR 12.4 ± 2.7 13.1 ± 1.6 .264 10.9 ± 5.4 .514
DB 14.1 ± 1.6 14.1 ± 3.0 .993 12.7 ± 2.2 .219
LB 14.4 ± 1.7 14.5 ± 1.2 .899 14.2 ± 2.4 .797
DL 14.4 ± 2.0 14.1 ± 1.7 .619 12.2 ± 4.0 .040*
OL 13.3 ± 1.6 14.2 ± 1.5 .243 12.8 ± 2.5 .646
K 13.2 10.8 13.0
P 12.0 16.0 16.0
Abbreviations: DB, defensive back; DL, defensive lineman; K, kicker;
LB, linebacker; OL, offensive lineman; P, punter; QB, quarterback; RB,
running back; SD, standard deviation; TE, tight end; WR, wide receiver.
aStudent t test comparing case presurgery and control preindex games/
season.
bStudent t test comparing case presurgery and case postsurgery games/
season.
6 Foot & Ankle International 00(0)
season fewer than controls. Although these differences in
performance are not statistically significant, they are clearly
clinically significant.
Interestingly, the RBs, OLs, and LBs also had the worst
RTS, with only 45.5% of RBs, 61.5% of OL, and 73.7% of
LBs returning to sport postoperatively. On the other hand,
QBs and special team players had an RTS of 100%. This
trend is similar to that found in a previous study looking at
the effect of injury on a career in the NFL in which LBs,
RBs, and OL were the most negatively affected by injury
and QBs and specialists were the least negatively affected
by injury.4
The majority (64%) of NFL players in the present study
sustained Achilles tendon rupture and underwent Achilles
tendon repair surgery during the offseason training camps.
No study has directly compared Achilles tendon ruptures
between the offseason training camps and regular season.
However, a prior study by Feeley et al demonstrated signifi-
cantly more injuries occurred during the first 2 weeks of
training camp compared to the final 3 weeks, with the
severity of injuries decreasing as the training camp
progressed.9 Additionally, a study of professional rugby
players found there to be significantly increased injuries in
the preseason compared to the regular season.3 Askling et al
found that a preseason program improved function and
decreased injury rate in professional soccer players, indicat-
ing that the addition of preseason strength and conditioning
training may be beneficial to elite professional athletes.2
These findings may have significant implications in the
occasional recreational athlete who may have limited
conditioning.
Figure 3. Performance scores by position before and after surgery compared to controls pre- and postindex.
, significant difference between pre- and postsurgery performance scores for cases; , significant difference between postsurgery and postindex
performance scores.
There are several limitations of this study. The use of
publicly available data to identify Achilles tendon tears
and repairs is prone to selection, reporting, and observer
bias. However, this method of data acquisition has been
used in multiple previous studies.1,6,8,18,19 Additionally,
the use of public data limits the ability to obtain the sever-
ity of the injury and the exact operative procedure (open
or percutaneous) being performed for Achilles tendon
repair. In this study, career length was not adjusted for
“time missed” for players who underwent surgery. Their
time in the league was in fact longer than reported; how-
ever, their seasons spent playing (ie, career length) after
surgery is accurate. Inherent to this type of study, there
are multiple unknown confounding variables such as pre-
surgical course and no direct physical contact or medical
records access to corroborate diagnosis. Other limitations
include the absence of patient-reported outcomes, incom-
plete follow-up and career length for players still in the
NFL, and inability to compare offensive lineman or spe-
cialist with performance scoring.
Conclusion
Following Achilles tendon repair, less than 75% of players
returned to the NFL. Postoperative career length was 1 sea-
son shorter than matched controls. No difference was
observed in the number of games per season played com-
pared to matched controls. Postoperative performance
scores were significantly worse for RBs and LBs compared
to preoperative, and LBs had significantly worse postopera-
tive performance when compared to matched controls.
Jack et al 7
Appendix A
Position Variables Collected
Quarterback Demographic: Age, experience
Presurgery and postsurgery (and index) variables:
Number of seasons, games
Total, per game, and per season variables
collected pre- and postsurgery (and
index): Completions, attempts, completion
percentage, passing yards, passing touchdowns,
interceptions, sacks, fumbles, rushing yards,
rushing touchdowns
Running back Demographic: Age, experience
Presurgery and postsurgery (and index) variables:
Number of seasons, games
Total, per game, and per season variables
collected pre- and postsurgery (and index):
Rushing attempts, rushing yards, rushing yards
per attempt, rushing touchdowns, receptions,
receiving yards, receiving touchdowns, fumbles
Tight end / wide
receiver
Demographic: Age, experience
Presurgery and postsurgery(and index) variables:
Number of seasons, games
Total, per game, and per season variables collected
pre- and postsurgery (and index): Receptions,
receiving yards, receiving yards per reception,
receiving touchdowns, fumbles
Offensive lineman
/ punter / kicker
Demographic: Age, experience
Presurgery and postsurgery (and index) variables:
Number of seasons, games
Defensive back
/ linebacker
/ defensive
lineman
Demographic: Age, experience
Presurgery and postsurgery (and index) variables:
Number of seasons, games
Total, per game, and per season variables collected
pre- and postsurgery (and index): Tackles,
assisted tackles, total tackles, sacks, safeties,
interceptions, forced fumbles, touchdowns,
passes deflected
Appendix B
Position Performance Score Formula
Quarterback (Passing yards ÷ 25) +(Passing
touchdowns × 4) + (Rushing yards ÷
10) + (Rushing touchdowns × 6)
Running back /
wide receiver /
tight end
(Receiving yards ÷ 10) + (Receiving
touchdowns × 6) + (Rushing yards ÷
10) + (Rushing touchdowns × 6)
Defensive players (Tackles) + (Assists ÷ 2) + (Sacks × 4) +
(Passes defended) + (Interceptions ×
5) + (Interceptions / Fumbles returned
for touchdowns × 6) + (Forced fumbles
× 3) + (Fumbles recovered × 2) +
(Safeties × 2)
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with
respect to the research, authorship, and/or publication of this
article. ICMJE forms for all authors available online.
Funding
The author(s) received no financial support for the research,
authorship, and/or publication of this article.
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