PHILADELPHIA (973espn.com) - The engine of Jim Schwartz's defense needs a part for the foreseeable future and that means there is an opportunity for someone to grab the brass ring.

Offseason back surgery has Tim Jernigan on the non-football injury list and uncertainty surrounds the big man's potential return from a herniated disk procedure with the more some estimates earmarking November for a potential return.

That scenario would wipe out about half the season for Jernigan leaving a gaping hole next to Pro Bowl star Fletcher Cox on the interior.  Meanwhile, there are darker scenarios which would have Jernigan sidelined even longer.

“I think so,” is all head coach Doug Pederson would say when asked if he was counting on Jernigan this season. “Yeah, again, he's another one that we've just got to be diligent with. Obviously, with the neck and everything, we've got to be careful.”

Pederson simply misspoke by saying "neck" instead of "back." The bigger issue has to do the uncertainty surrounding the veteran and how the Eagles will go about replacing him.

Last season, they would have just inserted Beau Allen, a workman-like player who excelled as a run stuffer. This time around they have an arguably better option in free-agent pickup Haloti Ngata but one that is also 34 and coming off a season in Detroit cut short by a biceps tear.

Through the first seven practices of training camp, third-year man Destiny Vaeao, a former undrafted free agent out of Washington State, has been working with the first-team in Jernigan's spot.

"I liked where he was coming out of training camp last year," defensive coordinator Jim Schwartz said when discussing Vaeao on earlier this week. "Unfortunately, he got hurt in the first game, and then he had to play with that cast on the rest of the year. So, this is a big year for him, just sort of putting it all together. I really liked where he came out of camp last year. He's a little bit bigger now, but not overweight. He's just bigger. He's just matured a little bit more. Put a little bit more weight on."

Weight isn't an issue for Nagata, the 340-pound three-time Pro Bowl selection who has been one of the best run-stoppers of his generation.
At this stage of Ngata's career, however, he almost certainly has to be placed on a pitch count with the idea of still garnering meaningful two-down reps late in the season, something that was exemplified Thursday when the Eagles gave Ngata a so-called veterans day.

To date both big-name veterans on the D-Line acquired in the offseason, Ngata and the versatile Michael Bennett, have started out by working with the second-team as Schwartz gets them familiar with how the Eagles so things.

"Right now, particularly guys like Michael and Haloti, we're just sort of melting them into the scheme right now," Schwartz explained. "I don't want to say just easing them in, but they're sort of melting in, I guess, and just let them get their feet under them."

Last year the Eagles' defensive line was arguably the deepest in football with Brandon Graham, Cox, Jernigan and Vinny Curry serving as the starters with Graham then kicking inside next to Cox in pass-rush situations and Chris Long and Derek Barnett inserted on the edges, the former taking Graham's spot at left end and the latter coming in for Curry. Allen was the third man on the interior with Vaeao also getting a handful of snaps each week when healthy.

With Jernigan unavailable and both Curry and Allen in Tampa, things have to be tweaked but the talent on hand in arguably greater with Bennett and Ngata. The only question is how Schwartz decides to dish out the playing time.

The guess here is that when Graham is cleared from offseason ankle surgery he will again start on the left end with Cox and likely Ngata as the two-down run stuffer in the middle. From there Bennett and Barnett will likely split the right end position with Long serving in his familiar nickel rush role as Graham slides inside to replace Ngata. Vaeao, meanwhile, will have an increased role as the third man in the middle.

However it shakes out, Schwartz has what he wants -- versatility.

"Last year we had Brandon Graham that played a lot inside and outside," the DC said. "Vinny Curry could have also done that for us. Now, obviously, Vinny's gone. So, a guy like Mike can come in and do those kind of things for us also. And that's important. One thing that we did a little bit of last year, you saw Fletch [Eagles DT Fletcher Cox] outside a little bit at times last year, and it gives us flexibility to do those kinds of things too."

-John McMullen covers the Eagles and the NFL for 973espn.com. You can reach him at jmcmullen44@gmail.com or on Twitter @JFMcMullen