Per ESPN.com.
This is somewhat surprising given the season he just had and the youth on the Packers.
But, he cites mental fatigue. Once you lose your focus or your competitive drive, it's time to hang 'em up.
I'll miss watching him play.
Singler is IRON
I STILL GOT IT! -- Ryan Kelly, March 2, 2013
Somewhere, Peter King and John Madden are together, sobbing uncontrollably. How can football possibly recover from this?
Sorry, couldn't resist. Vikings fan here.
A great quarterback and, I suspect, his stature will increase during the next decades.