Andrew Luck's final pass as an NFL quarterback didn't come in a Super Bowl. It didn't come in a Pro Bowl, or in a playoff game. It didn't even come in a regular-season game. Instead, it came during pregame warmups on Saturday night, with Luck -- wearing street clothes as he continues to recover from multiple injuries -- throwing passes to teammates only hours before officially announcing his retirement. 

At 29 years old, Luck said that the never-ending cycle of injuries, rehab, then more injuries has led to his difficult decision to retire 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.''

The former Colts quarterback and No. 1 pick in the 2012 draft now joins the following list of notable NFL players who decided to retire at relatively early ages. 

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. 

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. 

Rob Gronkowski 

While he retired early (just months shy of his 30th birthday), Gronkowski's retirement was not completely unexpected. While he was still a major contributor on New England's 2018 championship team, injuries had significantly taken their toll on Gronk, who saw a major dip in production last season after having an All-Pro campaign in 2017. A surefire future Hall of Famer, he retired with 521 receptions for 7,861 yards and 79 touchdowns in 100 career regular season games. He also retired with three Super Bowl rings.

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, will be eligible for induction into Pro Football Hall of Fame in 2021.  

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

Barry Sanders 

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 eligible for induction into the Pro Football Hall of Fame in 2020.