Indianapolis Colts star Andrew Luck caught a lot of people off guard when he retired from the NFL on Saturday, but he is not the first player to do that.
In this league, the wear and tear can take a toll on a player, several stars decided to hang up their cleats unexpectedly.
We look at a few over the years we did not see coming.
Most surprising retirements in NFL history
Jim Brown, Cleveland Browns, RB, 1966
The original surprise came when Jim Brown, the NFL's MVP in 1965, announced that he was hanging up his cleats two months before the start of the 1966 season. Brown retired as the NFL's all-time leading rusher and was coming off a season where he rushed for 1,544 yards and 17 touchdowns. He stepped away at the peak of his game and moved on to become a movie star and true ambassador for the game.
Overall, Brown won.
Barry Sanders, Detroit Lions, RB, 1999
Along the same line as Brown, Barry Sanders was at the top of his game when he decided it was enough. He rushed for 2,000 yards in 1997 and eclipsed 1,400 in 1998. But after just 10 NFL seasons he decided to step away. He was playing behind an abysmal offensive and was repeatedly being stopped in the backfield.
The league lost a great entertainer that day.
Chris Borland, San Francisco 49ers, LB, 2015
Chris Borland was a pleasant surprise as a rookie with the 49ers and a player who the team thought would be a key part of their defense. But, citing concern over head injuries, he retired in 2015 and left San Francisco scrambling to fix the middle of their defense. Borland tallied more than 100 tackles in his first season and really has not done much since leaving the NFL.
Calvin Johnson, Detroit Lions, WR, 2016
The 6-foot-5, 237-pound wide receiver might have been the most gifted pass catcher in NFL history. Calvin Johnson's size suggested he should have been less athletic than he was, but his 4.3-second, 40-yard-dash speed was absolutely impossible to contain. But four years after he nearly hit 2,000 receiving yards, he announced his retirement. Johnson was coming off a 1,214-yard, nine-touchdown season and was still one of, if not the best, receiver in the NFL.
This was a shock to football fans everywhere.
Joe Thomas, Cleveland Browns, OT, 2018
For a man who never missed a start until midway through the 2017 year, it was hard to believe he was done. Joe Thomas made the Pro Bowl in every single year he played before an injury ended his final season and he was still an amazing offensive tackle. But he had had enough football and has since moved over to the media business and has been an instant success.