Palmer, 38, saw his final season come to an abrupt end when he suffered a broken left arm against the Rams in Week 7.
Drafted first overall by Cincinnati in 2003, Palmer spent eight seasons with the
He was a three-time
In an open letter to fans posted Tuesday on Twitter, Palmer wrote: "Over the years, I've had teammates who decided to hang it up and I would ask them how they knew when it was time to walk away. The answer was almost always the same: You just know.
"For me that time is now. Quite simply, I just know."