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Aaron Donald made a lot of quarterbacks happy on Friday when he officially announced his retirement from the NFL. Donald, the Los Angeles Rams' standout defensive tackle, retires as one of the greatest players in NFL history. 

How great was Donald? He and Hall of Fame running back Barry Sanders are the only players in NFL history to play at least 10 seasons and be selected to the Pro Bowl each year (h/t ESPN). Donald was a 10-time Pro Bowler, eight-time All-Pro and three-time Defensive Player of the Year during his decade with the Rams. 

The 32-year-old Donald is retiring while still being one of the league's top players. He was named to the Pro Bowl yet again last year while helping the Rams secure a playoff berth. By retiring now, Donald is choosing to go out on his terms, a rarity in pro sports. 

Donald isn't the only notable NFL player to retire at a relatively early age. Here's a look at some others.

Andrew Luck 

Andrew Luck made the stunning decision to retire just a few weeks before the start of the 2019 NFL season at age 29. Getty Images

At 29 years old, Luck said that the never-ending cycle of injuries, rehab, then more injuries led to his difficult decision to retire in 2019 after 86 regular-season games. After not missing a game during his first three seasons, Luck missed nine games in 2015 after sustaining an injured shoulder, a lacerated kidney and a partially torn abdominal muscle. After playing in pain throughout the 2016 season, he missed the entire 2017 after needing multiple surgeries to repair his injured shoulder. 

Luck returned in 2018, enjoying one of his most productive seasons while guiding the Colts to the second round of the playoffs. Luck, who was named to the Pro Bowl last season, was also named the NFL's Comeback Player of the Year. But after sustaining two more injuries this offseason, he decided to honor a promise he made to himself in 2016: that he would not go through another season of unknowns with regard to his injuries and playing status. 

"I've been stuck in this process," Luck said during his retirement press conference. "I haven't been able to live the life I want to live. It's taken the joy out of this game ... the only way forward for me is to remove myself from football.

"This is not an easy decision. It's the hardest decision of my life. But it is the right decision for me.''

Tiki Barber

While Barber's career wasn't short by any means, his decision to retire after the 2006 season -- his 10th season with the New York Giants -- was odd considering that he was playing the best football of his career when he decided to step away from the game at 31 years old. After not earning a single Pro Bowl selection during his first seven seasons, Barber earned three Pro Bowl selections and an All-Pro nod during his final three seasons. In 2006, his final season, Barber rushed for 1,662 yards for a 5.1 yards per carry average. He also amassed 2,127 all-purpose yards, the third straight year that saw him eclipse the 2,000-yard barrier. 

Despite losing Barber, the Giants would go onto win the Super Bowl in 2007. 

Jim Brown

The NFL's first "shocking" retirement belonged to Brown, who was just 29 years old when he stepped away following the 1965 season. Brown, the league's reigning rushing champion who was a year removed from leading the Browns to their last NFL title, decided to pursue acting instead of prolonging his NFL career. Despite his early retirement, Brown's 12,312 career rushing yards stood as the highest total in NFL history until Walter Payton passed him in 1984. Brown, a member of the Pro Football Hall of Fame, is still regarded by many as the greatest running back in NFL history. 

Earl Campbell 

The NFL's rushing champion during each of his first three NFL seasons, Campbell, one of the most physical running backs in NFL history, was out of football before his 31st birthday, calling it a career after the 1985 season. While injuries did not force him out of the game, Campbell, a career Oiler before being traded to the Saints before the start of the '85 season, was not the same player in New Orleans after seven years of wear and tear on his body in Houston. Despite his relatively short career, Campbell was inducted into the Pro Football Hall of Fame in 1991, his first year of eligibility. He was named to the NFL's 100th Anniversary Team in 2019. 

Terrell Davis 

A two-time Super Bowl champion as well as a former league and Super Bowl MVP, Davis retired before the start of the 2002 season at the age of 29. Davis, who still holds the NFL record for the most yards rushing in a single postseason, sustained a serious knee injury four games into the 1999 season. While he returned to play the following two seasons, Davis decided to go out on his own terms heading into the '02 season. Davis, despite appearing in just 78 regular season games, was inducted into the Pro Football Hall of Fame in 2017. 

Calvin Johnson 

One of this century's best receivers, Johnson was just 30 years old when he hung up his cleats for good following the 2015 season. Injuries largely contributed to his decision to retire after nine seasons in Detroit. Johnson, a six time Pro Bowler who twice led the NFL in receiving yards, was inducted into the Pro Football Hall of Fame in 2021. 

Luke Kuechly 

A five-time All-Pro, Kuechly was 28 when he hung up his cleats in January of 2020. Injuries was the main reason why Kuechly decided to retire after eight seasons, seven Pro Bowl selections and a spot on the Hall of Fame All-2010s Team. Kuechly won Defensive Rookie of the Year in 2012 and Defensive Player of the Year in 2013. Two years later, he helped the Panthers win 15 regular season games en route to an NFC championship. 

"I've been fortunate enough to have the opportunity to play this game since I was in fourth grade," Kuechly said during his retirement announcement. "I've been with the Panthers now for eight years and it's never the right time to step away but now is the right time for me. It's a tough decision, I've thought about it a lot and I think now is the right chance for me to move on."

Barry Sanders 

Barry Sanders retired less than two years after rushing for 2,053 yards and winning league MVP honors.  Getty Images

Luck's retirement came 20 years and one month after arguably the most shocking retirement announcement in NFL history. Sanders, just 31 years old and a year removed from his 2,053-yard rushing season, announced his retirement just before the start of the 1999 season. Now a member of the Pro Football Hall of Fame, Sanders was just 1,457 yards away from breaking Walter Payton's all-time rushing record, a record that would ultimately be broken by Emmitt Smith in 2002. 

"The reason I am retiring is simple: My desire to exit the game is greater than my desire to remain in it," Sanders wrote in his retirement statement. "I have searched my heart through and through and feel comfortable with this decision."

Gale Sayers 

Sayers, the Chicago Bears running back who had arguably the greatest rookie season in NFL history, retired after the 1971 season at the age of 28. Injuries had taken their toll on Sayers, who was a four-time All-Pro and five-time Pro Bowler during his first five NFL seasons before injuries limited him to just four games during his final two NFL seasons. Despite appearing in just 68 games, Sayers, a two-time NFL rushing champion, did enough during his seven-year career to earn induction into the Pro Football Hall of Fame. 

Lynn Swann

A valuable member of Pittsburgh's 1970s dynasty, Swann, the first receiver to be named the MVP of a Super Bowl, retired at age 30 after nine NFL seasons. While a long history with head injuries was thought to play a role in his early retirement, Swann told NFL Films during a 2017 documentary that the opportunity to get into broadcasting on a full-time basis was the main reason why he hung up his cleats for good before the 1983 season. While he waited nearly 20 years, Swann's career was eventually immortalized in Canton in 2001. 

Patrick Willis 

One of the best defensive players of his era, Willis was 30 when he announced his retirement during the 2015 offseason. A seven-time Pro Bowler and five-time All-Pro, Willis' early retirement was largely due to a nagging injury to his big toe that caused him to miss most of the 2014 season. Willis, who played a large role in San Francisco's run to Super Bowl XLVII, will be inducted into the Pro Football Hall of Fame this summer. 

Ali Marpet 

After seven seasons, 107 games, a Pro Bowl nod and a Super Bowl victory, Ali Marpet decided to retire after the 2021 season. The Buccaneers' longtime offensive lineman hung up his cleats at age 28. Marpet reportedly made this decision due to concerns for his overall health. He retied after finishing his career with a Super Bowl win (2020) and his first Pro Bowl berth (2021).