Indianapolis Colts quarterback Andrew Luck announced his retirement from the NFL Saturday night, bringing an abrupt and shocking end to his once-promising career.

“I am going to retire,” Luck told reporters following the Colts’ 27-17 preseason loss to the Chicago Bears. “This is not an easy decision. It’s the hardest decision of my life. But it is the right decision for me.”

After dealing with a leg injury throughout training camp and the preseason, Luck is described as mentally worn down and ready to walk away.

The news comes as a complete shock: Luck has been widely regarded as one of the sport’s prototypical franchise quarterbacks since his days at Stanford, and when the Colts selected him with the first overall pick in the 2012 NFL draft, they believed they had an All-Pro quarterback for years to come.

Luck had great success early in his career, leading the Colts to the playoffs in each of his first three seasons.

But a shoulder injury cost him the entire 2017 season, and although he played well in 2018, he wasn’t the same quarterback. The injury had kept Luck out of all of the team’s offseason workouts and all but three training camp practices, and put Luck’s status for the Colts’ Sept. 8 season opener against the Los Angeles Chargers in doubt

Luck’s career will be remembered by a lot of what-ifs? Like LeBron James in the NBA, Luck came into the NFL with great hope and promise. He leaves now with a ton of question marks.