The answer was nearly always the same: "'You just know.'" Palmer said in a letter published by the Cardinals.
On Tuesday, Palmer announced his retirement in an open letter to Cardinals fans.
Palmer ends his career 12th on the all-time rankings with 294 touchdown passes.More news: Mariah Carey Slays on NYE, Warms Up with Some Hot Tea
The Cardinals' offseason of change won't be limited to their head coaching position. For 15 years I've been able to play quarterback in the National Football League, and it's been the most incredible experience in my life. Those are details that I know fade with time. "There wasn't one second that I took it for granted or failed to appreciate what a tremendous privilege it is".
The retirement of Palmer, though not unexpected, leaves the Cardinals without a quarterback on their roster.
He had a stellar season, with career highs in yards, touchdowns and quarterback rating, and was named a Pro Bowler for the third and final time.More news: Iran restricts social media networks used by protesters
Larry Fitzgerald has still not announced whether or not he will return for another season.
His relationship with the Bengals ended poorly, with Palmer requesting to be traded after the 2010 season.
Palmer, 38, was selected by the Cincinnati Bengals with the first overall pick in the 2003 NFL Draft, having won the Heisman Trophy at USC.More news: 2017 at the Box Office
Palmer had two major knee injuries in his career, tearing the ACL in his left knee twice, once in 2006 and again in 2014. Palmer finished the 2011 season in Oakland and played there in 2012 before the Raiders traded him to the Cardinals in April 2013.