TERRE HAUTE, Ind. (AP) — Quinn Pitcock spent a lifetime preparing to play pro football.

It took one year in the NFL with the Indianapolis Colts for Pitcock to decide he wanted to do something else. The defensive tackle has decided to retire at age 24.

"After much deliberation and careful thought, Quinn resolved to retire from the NFL," agent Brad Leshnock said in an e-mail confirming Pitcock's decision.

Leshnock said Pitcock informed team officials of his intentions last week.

The former Ohio State player did not report with the rest of the Colts to Rose-Hulman Institute of Technology last Thursday and was placed on the Colts' did not report list.

The move still surprised the Colts, who expected the 2007 third-round pick to be a contributor in their regular defensive line rotation behind starting tackles Ed Johnson and Keyunta Dawson.

Coach Tony Dungy and team president Bill Polian even told Pitcock he could have more time to reconsider. Should he decide to come back later, Dungy said the Colts would welcome him back.

"We want to leave the door open for him because I have been aware of people changing their minds," Dungy said in a not-so-subtle reference to the ongoing saga between Brett Favre and the Green Bay Packers. "We told him to take as much time as he needed."

Officially, the Colts have not announced the retirement because Polian said the team has not received the paperwork. But that now seems like a formality.

"Quinn is grateful for the opportunity the Colts gave him, and he wishes his teammates and the whole organization nothing but the best going forward," Leshnock said.

The 6-foot-2, 299-pound Pitcock was injured early in training camp last season, but was healthy enough to play in nine games. He made 30 tackles and became a bigger part of Indianapolis' defense after former league sacks champion Dwight Freeney went down with a season-ending foot injury in November. The Colts allowed the fewest points in the NFL (262).

Now they may try to fill the void left by Pitcock with players already on the roster, something the Colts have excelled at in recent years.

Last August, a season-ending knee injury to defensive tackle Anthony McFarland opened the door for Johnson, an undrafted rookie who won the job and started all 16 games. McFarland was waived in February.

And when starting linebacker Rob Morris underwent season-ending knee surgery in October, the Colts plugged in little-known Tyjuan Hagler, who started seven of 12 games and was the projected strong-side starter this season. But Hagler opened camp on the physically unable to perform list with a torn pectoral muscle and may not return until October.

Now second-year linebacker Clint Session has a chance to earn the starting job.

"It's pretty much raised the level of my game a lot," said Session, who has been practicing with the starters. "There are a lot of good players out there, Pro Bowl-type players like (safety) Antoine Bethea."

Injuries have already left the Colts short-handed. Six players, including Hagler, are on the physically unable to perform list. The others are Freeney, two-time league MVP Peyton Manning, 2007 NFL defensive player of the year Bob Sanders, starting guard Ryan Lilja and rookie tight end Tom Santi.

Manning had surgery July 14 to remove an infected bursa sac, and all except Hagler are expected to be healthy for the Sept. 7 regular-season opener against Chicago.

A handful of other veterans are practicing just once a day.

Still, with seven defensive tackles left on the Colts' 80-man training camp roster, including Johnson, Dawson and Raheem Brock, who has been getting more work at defensive end this summer, Dungy isn't fretting about the loss of Pitcock.

"It is a tough situation because we really felt Quinn had the things we were looking for," Dungy said. "But football is a tough game and if you're not into it 100 percent, it's tough to play. It's always an opportunity for someone and usually they come through, so we're hoping that's what happens."