Tony Dungy will retire after seven seasons in Indianapolis and Jim Caldwell will take over as Colts coach, one of his assistants confirmed Monday.
Receivers coach Clyde Christensen said Dungy informed the staff of his decision earlier in the day.
"I think there was an intensity in there and it was emotional," he said. "We all felt like it was going to happen one of these years."
Dungy met with players throughout the day to say goodbye.
The move comes a little more than a week after the Colts were eliminated from the playoffs. An afternoon news conference was scheduled to make the announcement.
Repeated messages were left by The Associated Press on Dungy's cell phone.
FoxSports.com was the first to report Dungy's decision.
The plan to have Caldwell replace Dungy was put in place last year when the coach pondered retirement. Caldwell joined Dungy's staff in Tampa Bay in 2001, then moved with Dungy to the Colts in 2002 and was the quarterbacks coach. A year ago, Caldwell was elevated to associate head coach though he continued to coach Peyton Manning and Jim Sorgi.
Dungy has spent the past five years debating whether to leave football, each year taking about a week to meet with his family, which now lives in Tampa. He has always said when he left, he would not return.
"You know, I told my wife I'm sad, but I don't know why I'm sad," Christensen said. "To see a guy be happy and make a good decision, you should be happy. I guess I was just hoping for one more year with him."
Dungy has always listed his priorities as faith, family and football, and returned to coach in 2008 when the Colts opened the new Lucas Oil Stadium only after team owner Jim Irsay agreed to let Dungy use a private jet to commute home.
The decision ends a tenure in Indianapolis during which Dungy became the first black coach to win a Super Bowl. He reached the playoffs all seven seasons, winning five division titles and appearing in two AFC title games.
Dungy finishes his career as the Colts' franchise leader in victories, going 85-27 in the regular season and 7-6 in the playoffs.
But Dungy's teams were also eliminated from the playoffs four times without winning a game, including the past two seasons after winning the Super Bowl -- prompting some to speculate that Dungy's indecision may have hurt the Colts' focus.
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.