Quite a career, No. 12. Colt McCoy, a two-time All-American, two-time Walter Camp Football Foundation Player of the Year, two-time Heisman Finalist, the 2009 Big 12 Offensive Player of the Year, the 2009 Maxwell Award winner, and the 2009 Davey O’Brien Award winner who went on to a 14-year NFL career announced his on-field retirement on Monday in a YouTube video posted on Underdog Originals. [Sign up for Inside Texas and get the BEST Longhorns scoop!] McCoy, whose No. 12 at Texas is one of six retired numbers, will join NBC Sports’ coverage of Big 10 football. Per NBC, he will be a game analys…