PHILADELPHIA -- He won the Heisman Trophy. He was the No. 1 pick in the NFL draft. He tore his anterior cruciate ligament twice.

He could be either Sam Bradford or Carson Palmer, the two men who will start at quarterback Sunday when the Philadelphia Eagles host the Arizona Cardinals.

Palmer, 35, won the Heisman for USC in 2002 and was the first pick in the 2003 NFL draft.

Bradford, 28, won the Heisman as a sophomore at Oklahoma in 2008 and was the first pick in the 2010 NFL draft.

After six years with the Cincinnati Bengals, Palmer asked to be traded. When the Bengals declined, Palmer said he would retire. He held out until the middle of the 2011 season, when the Bengals agreed to trade him to the Oakland Raiders.

After five years with the St. Louis Rams, Bradford was traded to the Eagles.

There is a lesson in here about time, and its role in allowing NFL quarterbacks to reach their full potential.

Eagles quarterback Sam Bradford has won his last two starts since returning from injury. AP Photo/Michael Perez

“It takes a long while to play quarterback in this league,” Eagles coach Chip Kelly said. “There are so many things you have to get. When we got Sam, we knew with any quarterback, it’s going to take time.

“Name any quarterback playing at a really high level now, and they’ve been playing in the same system for years. Not for months. Sam has been playing in our system for months.”

Kelly rattled off names like Aaron Rodgers, Tom Brady and Ben Roethlisberger. Palmer is a little bit different. Since he got to Arizona in 2013, his record as a starter is 27-8 with a passer rating of 94.4. It didn’t take him years in coach Bruce Arians’ offense.

But Palmer still put in the years.

“He’s played a ton of football,” Kelly said. “The wealth of experience that Carson brings to Bruce’s offense is kind of unparalleled. He’s the guy that’s pushing the whole offensive system right now.”

Palmer will turn 36 later this month. He has never won a playoff game. During eight seasons in Cincinnati and Oakland, his record as a starter was 54-67. The best years of his career have been in Arizona, after he turned 33 years old.

Kelly has previously compared trading for Bradford to the New Orleans Saints’ signing of Drew Brees. The former San Diego Chargers quarterback was available only because of an injury to his throwing shoulder. The Saints took a chance on Brees, who has gone 92-63 and won a Super Bowl.

Bradford’s resume looks more like Palmer’s. The challenge for Kelly and the Eagles is to make sure that Bradford can accelerate the second part of his career. That means staying in Philadelphia and growing in Kelly’s offense, not moving on to a third team.

That is Kelly’s plan.

“We’ve always wanted Sam here,” Kelly said. “We wouldn’t have traded for him if we thought he was going to be here for a year.”

Bradford has exactly three games (plus playoffs, if there are any) remaining on his contract. The Eagles and Bradford’s agent discussed a contract extension, but those talks ended at the start of the regular season.

Bradford went 4-4 as the Eagles’ starter in the first half of this season. He was leading in the Eagles’ Nov. 15 game against Miami when he was knocked out of the game with a concussion and separated left shoulder. The Eagles lost that game, as well as their next two with Mark Sanchez as their quarterback.

Bradford returned for the game against New England. He won his two starts since returning from the injury. Before each game, he addressed his teammates.

“I’ve seen Sam gain more confidence as the season’s gone along here,” Kelly said. “I think that’s just a natural maturation process.”

That takes time. The big question is how much time Bradford will have in Philadelphia.