Arizona Cardinals quarterback Carson Palmer has announced his retirement after a 15-year NFL career.
The 38-year-old's announcement comes two days after the end of the regular season and a day after Cardinals coach Bruce Arians made the same decision.
"Over the years, I've had team-mates who decided to hang it up and I would ask them how they knew when it was time to walk away," Palmer wrote in a statement.
"The answer was almost always the same: You just know."
The Cardinals finished the season with a 26-24 win over the Seattle Seahawks but their 8-8 record wasn't good enough for a spot in the playoffs.
Palmer's season and career actually ended in London in October, a broken arm suffered in the loss to the LA Rams at Twickenham bringing a premature end to his season.
Palmer was the No 1 overall pick at the 2003 NFL draft and played for the Cincinnati Bengals and the Oakland Raiders before joining the Cardinals in 2013.
2015 was his standout year, he threw for a career-high 4,671 yards and 35 touchdowns as the Cardinals went 13-3 before losing to the Carolina Panthers in the NFC Championship game.