THE EAGLES' story lines this spring are all about gambles. Chip Kelly is gambling on Sam Bradford's left knee and DeMarco Murray's durability and Jordan Matthews' upside and his own ability to oversee not just the execution of X's-and-O's, but the selections of Jimmys and Joes.

The biggest gamble, though, might be where he has chosen not to wager, and not to upgrade. There are no significant additions this spring to an Eagles offensive line that got pretty banged up a year ago and struggled even when intact, an offensive line that clearly did not live up to its billing as a team strength when last season began.

Think about it: Had they started the 2014 season as they had ended the previous one, LeSean McCoy might have at least come close to his 2013 rushing totals, Nick Foles might not have developed some bad habits, such as throwing off his back foot, Riley Cooper might even have caught more balls for more than 20 yards.

Foles also might not have had run for his life so much, been thrown to the ground as much, might not have broken his collarbone. He and McCoy might even still be here.

"I didn't think we weren't going to draft anybody," tackle Jason Peters was saying after yesterday's OTA at the NovaCare Complex. "But Chip believes in us, and I like that."

But why? Entering his 12th NFL season, Peters is 33 and coming off a bad December in which he was getting beat by the likes of Washington's Jackson Jeffcoat. Jason Kelce suffered a sports hernia early on and played at less than 100 percent when he came back. Evan Mathis is in a contract dispute. Allen Barbre, Andrew Gardner and Matt Tobin are still mostly unproven entities - at least empirically.

"But I thought Tobin was their best guard last year in training camp," Brian Baldinger, the NFL Network analyst and former Eagles offensive lineman, said yesterday. "Now, he got hurt, and he missed time. But he's an exceptional player. He runs real good."

That, apparently, is the key to Kelly's complacency, if it can be called that. There are 16 offensive lineman on hand. And while the Eagles can't keep all of them, they will all get a chance to see how they run inside of an offense predicated on quickness up front to operate at peak effectiveness.

"The one thing about this line, more than any other line in the league, is they run to get to the perimeter more than anybody," Baldinger said. "So while most lines are very static and just move the line of scrimmage, they don't really move the line of scrimmage - they just stretch it. And a lot of it is how they pull and get out on the perimeter. So your guards and center - Kelce is as good as anyone in the league right now - they've got to get out and run. They run these plays where they get two or three lineman running at a time - it's really difficult to defend. It opens up these huge holes."

The Eagles set franchise records in a slew of offensive categories last season, including points, touchdowns and first downs. Those records, though, hid some erratic performances, particularly down the stretch in consecutive December losses to Seattle, Dallas and Washington.

Kelce never fully recovered from the sports hernia, he acknowledged yesterday. Peters looked slow and perhaps even old in the December cold, something he acknowledged as well yesterday when he said: "There's a lot of stuff I think I can get better at. Toward the end of the season, I gave up a couple of sacks that I shouldn't have given up. So I'm here trying to clean things up."

Said Baldinger of Peters: "He's the key. He's got to be the anchor. He's their best player. Lane [Johnson] has done exactly what he was expected to do. He's the most athletic right tackle in the league. And he's got long arms and knows how to use them. He's good and he should get better this year. And people talk about the guards, but whether Mathis is here or not, I think they're going to be fine. Peters is the key."

To that point, Peters' position coach, Jeff Stoutland, raved about his offseason training and conditioning last week. Whether he can maintain that shape through the rigors of the long season might be as great an unknown as the quality of the line depth. But clearly Kelly has stood pat this offseason (so far), because he not only believes in Peters and the provens, but in his strength of numbers.

"I don't think it's as big of a gamble as people may make it out to be," Kelce said of Kelly's faith in his group. "Last year when we had a lot of injuries, the guys who went in proved physically that they can get the job done. We definitely took a step back. But that was more a cohesion thing.

"The more repetitions, the more comfortable they get playing with each other. We're going to be just fine. I think if they had to be thrust in again, they would do a much better job."

On Twitter: @samdonnellon