Dungy also spent six seasons in Tampa Bay, rejuvenating a moribund franchise and turning it into a perennial Super Bowl contender in the late 1990s and the early part of this decade. The 53-year-old coach left Tampa with a career record of 54-42 in the regular season becoming the winningest coach in franchise history there, too, and got the Buccaneers to the NFC title game in 1999.

He's the only coach in NFL history to produce six straight 12-win seasons and 10 consecutive playoff appearances.

Dungy's career, which includes an all-time league-high average of 10.7 regular-season wins, also included tragedy. In December 2005, his son, James, committed suicide while attending school in Tampa. He left the Colts for one game, then received the game ball from his players after they made a goal-line stand to beat Arizona in the season-finale.

The Colts' season ended two weeks later with a shocking loss to eventual Super Bowl champion Pittsburgh.

Dungy always said he intended to retire by the time he turned 50, but hung around longer because he enjoyed the game and the Colts players.

But his family priorities won out this time. His son, Eric, will be a high school senior in the fall, and those close to him thought Dungy wanted to accompany his son on college visits.

Caldwell's only other head coaching experience came at Wake Forest, where he went 26-63 from 1993-2000.