Early retirements are on the rise in the NFL, and over the past year, fans have been stunned by the decisions of several elite players in their prime who have decided to walk away from the game for various reasons. Several players in recent years have cited concussion-related issues as a reason for leaving football, a trend that is expected to continue as we learn more about CTE.

From Panthers star Luke Kuechly, who just announced his retirement in January after his eighth NFL season, to Hall of Fame talents who decided to walk away from the game in their prime, here are 22 NFL players who retired early:

1. Luke Kuechly

A seven-time Pro Bowler, five-time first-team All-Pro, Panthers linebacker Luke Kuechly was the 2013 NFL Defensive Player of the Year. He announced his retirement after his latest Pro Bowl campaign at the age of 28, after eight total NFL seasons in Carolina. Kuechly suffered multiple concussions over the course of his career, though he did not cite concerns over concussions when he announced his retirement on social media. “In my heart, I know it’s the right thing to do.”

2. Rob Gronkowski

It remains to be seen if Rob Gronkowski ever returns to the football field – he hasn’t ruled out a comeback, and Patriots fans would certainly love to have the dynamic tight end back. Gronkowski walked away from football at the age of 29, just after winning a third Super Bowl with New England. He’s already a Hall of Fame lock, with four first-time All Pro selections during his nine seasons in the league.

3. Andrew Luck

One of the most talented and lauded quarterback prospects to enter the league, Luck will be remembered for what he might have accomplished had he been able to remain healthy. Luck spent the summer recovering from a lower-body injury, but stunned the league by retiring in the preseason, with news of his decision breaking while he was on the sidelines during a Colts game. Luck, still only 30, played six seasons for the Colts.

4. Gale Sayers

Knee injuries forced Chicago Bears legend Gale Sayers to cut his career short, but he lead the league in rushing twice during his seven seasons in Chicago. Sayers was inducted into the Pro Football Hall of Fame at the age of 34, making him the youngest Hall of Famer ever.

5. Jim Brown

Regarded by many as the best running back of all time, Cleveland Browns icon Jim Brown averaged 100 rushing yards per game in seven of his nine NFL seasons, and retired at the age of 30 as the league’s all-time leader in rushing yards (12,312) and rushing touchdowns (106).

6. Barry Sanders

Detroit Lions running back Barry Sanders stunned the sports world when he retired in good health in his prime in 1998, having torched defenses in every one of his 10 seasons. A 10-time Pro Bowler, Sanders earned an NFL MVP award in 1997 after breaking the 2,000-yard mark in his best season as a pro. Sanders famously faxed his retirement announcement to a local newspaper, and has since said that he had lost some of his desire to play, which led to his decision.

7. Calvin Johnson

Lions superstar Calvin “Megatron” Johnson was an unstoppable wide receiver for the entirety of his career, which he voluntarily cut short in 2016 at the age of 30. A six-time Pro Bowler, Johnson twice led the league in receiving yards. He said he retired because the wear and tear of football had taken a toll on his body, and he could not perform to the level he expected. “I’m not going to go out there and not be 100 percent.”

8. Tiki Barber

Giants running back Tiki Barber surpassed the 1,500 yard mark in each of his final three seasons, scoring 27 touchdowns in that span, but left the game after the 2006 season and reportedly turned down a deal with the Giants worth $50 million to pursue a career as a broadcaster. Barber attempted to make an NFL comeback in 2011, but didn’t find a team.

9. Earl Campbell

The 1979 NFL MVP, Oilers running back Earl Campbell was one of the most dominant offensive players in the league in the late ’70s. He led the NFL in rushing yards for three consecutive seasons from 1978 to 1980, but after spending two years with the Saints, Campbell retired at the age of 31.

10. Billy Sims

Another Lions great who left in his prime, running back Billy Sims earned three Pro Bowl selections over his first four seasons, but suffered a devastating knee injury in 1984 that ended his career. He officially retired in 1986.

11. Terrell Davis

Along with quarterback John Elway, running back Terrell Davis carried the Broncos to back-to-back Super Bowl championships in 1998 and 1999, and earned Super Bowl MVP honors in a 31-24 win over the Packers, finishing the game with 157 rushing yards and three touchdowns. Davis was the NFL MVP in 1998 and rushed for 2,008 yards and 21 touchdowns that season. Serious knee injuries kept Davis on the sidelines for much of his final two seasons in Denver, and he retired in 2002 at the age of 29.

12. Chris Borland

A third-round draft pick by the 49ers in 2014, Chris Borland had an excellent rookie season in San Francisco – but retired from the league the following year, citing his concerns over his long term health. “From what I’ve researched and what I’ve experienced, I don’t think it’s worth the risk.”

13. Lynn Swann

A four-time Super Bowl champion with the Steelers and eventual Pro Football Hall of Famer, Swann accomplished more than most football players do in a lifetime over the course of nine seasons in Pittsburgh. He retired at the age of 30, still in his prime, and continued work as a broadcaster.

14. Patrick Willis

The 11th overall pick in the 2007 NFL Draft, 49ers linebacker Patrick Willis earned seven consecutive Pro Bowl selections in his first seven seasons in the league, but a toe injury derailed his season in 2014. The following spring, he announced his retirement at the age of 30.  “I felt like it was the perfect time. My body, everything. The stars aligned for me.”

15. Husain Abdullah

A free safety who played for the Vikings and Chiefs, Husain Abdullah retired in 2016 due to concerns over concussions. Abdullah explained his decision in a powerful piece he wrote for The Players’ Tribune. ” I did not retire out of fear. I retired because I had come to terms with my own medical history. If I had not suffered five concussions in my NFL career, maybe I would still be playing. But the fact is, I did suffer those concussions, and that tips the scale of risk to a point where the potential consequences outweigh the benefits for me.”

16. Anthony Davis

The 11th overall pick in the 2010 NFL Draft, 49ers offensive lineman Anthony Davis took a break from the league in 2015 to “allow [his] brain and body a chance to heal.” Davis made a comeback in 2016, but after suffering a concussion in practice, Davis retired a second time.

17. Rashard Mendenhall

A Super Bowl champion with the Pittsburgh Steelers, running back Rashard Mendenhall retired at the age of 26 after one season with the Cardinals. In a blog post explaining his decision, Mendenhall explained that he wasn’t comfortable risking his health to be an entertainer. “I tell them that I’ve greatly enjoyed my time, but I no longer wish to put my body at risk for the sake of entertainment. I think about the rest of my life and I want to live it with much quality.”

18. D’Brickashaw Ferguson

The No. 4 pick in the 2006 NFL Draft, offensive lineman D’Brickashaw Ferguson never missed a start in his 10 seasons with the New York Jets. Ferguson’s decision surprised fans, but in his retirement Ferguson explained that it had become more difficult to play to the level he wanted, and that he wanted to pursue other goals.

19. Christian Okoye

A two-time Pro Bowler and first-team All-Pro in 1989, Chiefs fullback Christian Okoye’s career lasted just five seasons. Okoye needed surgery on both of his knees after the 1992 season, but also felt that football had become “a job.”

20. Ickey Woods

Bengals fullback Ickey Woods will forever be remembered for his signature “Ickey Shuffle,” and also for his remarkable rookie season, during which he led the NFL in rushing touchdowns (15) and was a first-team All-Pro selection. Woods only played four seasons in the NFL, as repeated knee injuries resulted in his early retirement.

21. Brad Butler

After four seasons with the Bills, offensive lineman Brad Butler announced his retirement in 2010 at the age of 26. Butler explained that he simply wanted to focus on a different career. “My passion for education, country and community is something that I am ready to devote my full attention to. I believe the best way to pursue these spheres of interest is to step away from the game of football at this point in my life.”

22. Eugene Monroe

After seven seasons in the NFL, offensive tackle Eugene Monroe walked away from the game and wrote in The Players’ Tribune that he was “terrified” of what his future may hold due to the injuries he suffered. “The last 18 years have been full of traumatic injuries to both my head and my body. I’m not complaining, just stating a fact. Has the damage to my brain already been done? Do I have CTE? I hope I don’t, but over 90% of the brains of former NFL players that have been examined showed signs of the disease. I am terrified.”

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