PHILADELPHIA -- When explaining why he chose to gamble on oft-injured quarterback Sam Bradford, Philadelphia's Chip Kelly likes to reference the cautionary tale of another wildly prosperous college head coach whose NFL fate he is trying to avoid.

When with the Miami Dolphins in 2006, Nick Saban had the opportunity to sign Drew Brees as an unrestricted free agent. Saban passed because team doctors felt Brees couldn't mount a successful comeback from the shoulder surgery he underwent the previous season.

Brees continues to prove Miami's medical staff wrong each year while forging a Hall of Fame career with New Orleans. As for Saban, he retreated to the University of Alabama after a 6-10 campaign with the Dolphins.

More from FoxSports

Kelly strongly believes Bradford can enjoy similar success to Brees by rebounding from the knee injuries that have sidelined him for the better part of the last two seasons in St. Louis.

"The impact Drew had on the Saints was really what we studied," said Kelly, who traded 2014 starting quarterback Nick Foles to the Rams last March as part of a package for Bradford. "What would this league be like if Nick Saban had Drew Brees? Would Nick have ever gone back to Alabama?"

Now that he has taken the type of plunge that Saban didn't, Kelly must hope Bradford doesn't suffer the same fate as the quarterback Miami acquired instead of Brees -- Daunte Culpepper. The ex-Minnesota Vikings star never fully recovered from reconstructive knee surgery and was released after just one season despite having cost the Dolphins a second-round pick for his services.

The ongoing cynicism surrounding Bradford's ability to stay healthy is greater than it was for Culpepper upon his arrival in South Florida. Initially hurt on a sideline hit midway through the 2013 season, Bradford re-tore his left anterior cruciate ligament last preseason and spent the entire year on injured reserve.

Kelly, though, doesn't feel Bradford has a chronic knee problem. Kelly also points to the successful ACL recoveries of players like Eagles center Jason Kelce and wide receiver Jeremy Maclin, who left Philadelphia for Kansas City in free agency during the offseason.

"It's not like it was 15, 20 years ago," Kelly said. "I think the advances in all of medicine have really helped from an injury standpoint. I don't know if there's a way to prevent it. I also don't think this guy is more susceptible to it. When we look at his functional movement, we didn't think it's something where Sam is always destined to have this happen to him."

The Rams didn't have that same confidence. St. Louis got tired of waiting for Bradford to become the franchise quarterback they envisioned when making him the No. 1 overall pick in the 2010 draft, which led to the deal for a younger and healthier Foles.

Bradford himself was so devastated by last year's setback that he admits having considered retiring at the age of 27 before refocusing on his comeback.

"I knew what to expect physically. I think the second time around was a little tougher mentally," Bradford said Thursday after an Eagles walk-through practice. "You feel like you put all that work in and there's no reward for it. It was just hard to get back into that rehab mode. I knew I had that fight for the next nine, 12 months ahead of me again.

"But there were a few things I knew. There were going to be ups and downs. The first time, I just expected to get better every day and it doesn't work like that. There are some days you kind of hit a plateau. You're there for a few days and then (recovery) takes off again. I think I was prepared for that the second time, which helped."

Bradford also dedicated himself to other training while doing his rehabilitation with the Eagles. He is noticeably more muscular and leaner in the upper body now than when he returned from his first knee surgery in the 2014 preseason.

But while the Eagles are among the NFL's most innovative teams with their approach to sports science, Kelly knows it's also a matter of luck when it comes to Bradford avoiding another ACL tear.

"There are certain things where it doesn't matter what you do," Kelly said. "If you get hit a certain way, you're going to break a bone. There's not a sports science or training regiment that's going to help you with that. The ACL is a rotational injury. If your foot is planted the wrong way there's nothing you can do. You can only strengthen the muscle and base around it. But I think we did a real good job and Sam gets credit for it. He did it in terms of rehabbing."

Kelly and Bradford should feel relieved that the latter proved he wasn't made of glass during his preseason debut last Saturday against Baltimore. Bradford weathered a controversial low hit by Ravens outside linebacker Terrell Suggs to lead the Eagles on an 84-yard scoring drive in his lone series.

"I feel good right now," said Bradford, who was limited to individual drills in Philadelphia's offseason program. "We had a plan to be ready for training camp. I haven't missed any time because of my knee. You're never quite sure what to expect coming off the injury but I've been very pleased.

"At training camp, we get a lot of reps. We're out there for two-plus hours. I think the knee has handled the stress really well."

Bradford needs that practice time growing comfortable with an up-tempo offensive system far different than what he was accustomed to in St. Louis.

"There are not many people if anyone else doing what we're doing as far as the style of offense we're running," Bradford said. "When I first got here, I was kind of like, 'What's going on? What are they doing?' But you sit down and you learn why and when [Kelly] explains it you're like, 'That makes a lot of sense.'"

Bradford has some other things working in his favor as he tries to regain the form that helped him enjoy what was turning into a breakthrough 2013 season with St. Louis before his injury.

Extra attention: For the first time, Bradford is playing under a head coach with an offensive background. His two head coaches in St. Louis (Steve Spagnuolo and Jeff Fisher) were defensive specialists.

"For him to sit in quarterback and install meetings, it's been really cool," Bradford said of Kelly. "I've never really had that experience before."

Reunited and it feels so good: Bradford is reunited with Eagles offensive coordinator Pat Shurmur. The latter held the same position with the Rams during Bradford's rookie season before leaving to become Cleveland's head coach in 2011.

"The nice part about that is if I don't understand something or it's just not clear to me, (Shurmur) can revert to what we did in St Louis if it's similar and say, 'Remember when we ran this play and made this read?'" Bradford said.

"Usually we have one word and it tells everyone what to do. But if you do look at some of the concepts, some of them are fairly similar to what we did with Pat in the West Coast (system). It might not be said the exact same way but if you look at where guys are finishing, their end spots are very similar as far as some of the spacing patterns."

Help is here: Bradford is surrounded by a far better supporting cast of skill-position players than at any point during his five seasons in St. Louis. Bradford never played with a Rams wide receiver or tight end that tallied more than 700 receiving yards in a single season. At least four of his Eagles targets – tight end Zach Ertz, running back Darren Sproles, and wide receivers Jordan Matthews and Nelson Agholor – have the potential to exceed that total in 2015.

Bradford also should be backed by a strong ground attack featuring 2014 NFL rushing leader DeMarco Murray and former San Diego Chargers starter Ryan Mathews.

"When we get out on the practice field and I look from right to left, we've got playmakers all over the board," Bradford said with a smile. "We'll run three plays and they'll rotate the second group in there with us. We've got five more playmakers coming onto the field.

"Not only (that) but we're deep at every position. And I think the tempo we play at is going allow us to keep guys fresh and constantly put pressure on the defense."

When it comes to pressure, nobody will be feeling it more than Kelly if Bradford doesn't pan out. As part of his major offseason roster overhaul since assuming personnel power, Kelly made acquiring a "special" quarterback his top priority. Those types of passers are rarely available in free agency unless they're damaged goods like Brees of Peyton Manning when he was coming off 2011 neck surgery. The Eagles also weren't in position to jump almost 20 spots in this year's draft to select a building block like Jameis Winston or Marcus Mariota, who was one of Kelly's quarterbacks while at the University of Oregon.

"Now is there a risk in take injured player? Yeah. Does every player turn out be Drew Bees or Peyton Manning? No," Kelly allowed. "But with our research and doctors, we felt very comfortable with the situation when we had a chance to go get somebody like Sam who we believe is elite when healthy.

"Winning 10 games and not winning a playoff game isn't good enough for us. For us to go farther than what we have the past two years, we really felt this was a maneuver we had to make. It's been good so far but we still got a long way to go with Sam."

It's now on Bradford to prove he can last for the long haul.

Chip Kelly and Sam Bradford were interviewed by Alex Marvez and co-host Bill Polian on SiriusXM NFL Radio