INDIANAPOLIS - The Eagles have been negotiating with Beau Allen on a contract extension this offseason, according to NFL sources.

Extending the fourth-year defensive tackle would fall in line with the team's philosophy of retaining its own talent, especially at an affordable price. But in this case it would also suggest that the Eagles are preparing for the likelihood that homegrown Bennie Logan will walk via free agency.

It wouldn't come as a huge surprise if the defensive tackle were to leave. The salary cap continues to rise. Teams have money to spend - an estimated total of $1.3 billion - and the Eagles are one of four teams with just around $10 million or less in cap space. They already have a significant amount allocated to the defensive line, and with so many other greater needs, keeping Logan may not be practical.

But that doesn't mean the Eagles still don't have problems at defensive tackle. When given the opportunity to start for the injured Logan last season, Allen was solid. But would he be a viable option to play alongside Pro Bowler Fletcher Cox over a full season?

"We're excited about Beau, both in his ability to be powerful in the run game but also his athleticism to work edges," Eagles executive Howie Roseman said Wednesday at the NFL combine. "He has pass-rush moves. With an increased opportunity, we think he'll be an even better player to our team."

In three starts and an average of 51 snaps a game, Allen registered nine tackles, three hurries, and a fumble recovery. He didn't have a sack. In 13 other games and an average of 20 snaps per game as a backup, Allen notched 23 tackles, four hurries, and a half-sack.

Logan, by comparison, had more success as a pass rusher but only in the first four games before he suffered a groin injury (eight tackles, two sacks, five hurries, and a forced fumble). He was not the same player when he returned for the final eight games (23 tackles, three hurries, a forced fumble, and a half-sack).

When healthy, Logan has been a force against the run. And at least early last season, as he transitioned to a one-gap 4-3 front, he proved that he could thrive in an attacking defense. There's more money in free agency for 4-3 tackles than there is for 3-4 ends/nose tackles, but Logan's versatility is another reason the Eagles will have a hard time matching other offers.

"He has been a great player for us since he walked in the door," Roseman said of the 27-year-old Logan. "Huge contributor. Great character. Works hard. You try to keep as many good players as you can."

Selected in the third round of the 2013 draft, Logan became the starting 3-4 nose tackle midway through his rookie season. He had only three sacks in his first three seasons, but the scheme often required him to fill two gaps, read, and then react.

That being said, Logan isn't a premium pass rusher. But no top-tier inside rushers are expected to reach free agency, especially after the Panthers placed their franchise tag on Kawaan Short. The Cardinals' Calais Campbell is of that caliber, but he will turn 31 before the season and has played exclusively in a 3-4 front.

The Chiefs' Dontari Poe and the Ravens' Brandon Williams will probably be the two highest-paid free-agent defensive tackles this offseason. But they have been predominantly run-stopping 3-4 interior linemen.

If the Eagles were looking to replace Logan in free agency, the Saints' Nick Fairley, the Redskins' Chris Baker, or the Giants' Johnathan Hankins would be options. But why go in that direction when you could just keep Logan at a likely comparable price?

It's difficult to project the contract numbers for Logan, but the bidding could get steep. The defensive tackle market is light, 19 teams have more than $30 million in cap space to spend, and Logan is in his prime years.

The Eagles could have saved themselves the grief by extending Logan last offseason, but Roseman committed nearly $250 million to Cox, Lane Johnson, Vinny Curry, and Zach Ertz. The numbers are likely to change, but the Eagles have $34.25 million of their salary cap devoted to their top four defensive linemen (Cox, Curry, Connor Barwin, and Brandon Graham) in 2017.

The importance of the line in defensive coordinator Jim Schwartz's scheme cannot be overstated, but Cox's $102.6 million contract could hamstring the Eagles in some ways. He earned his second straight Pro Bowl nod, but his 2016 season was a mild disappointment. It was very good by most estimates, however, and he's still only 26.

Allen, who was selected in the seventh round in 2014, won't turn 26 until November. There was some concern that the 6-foot-3, 327-pound former nose tackle would struggle adjusting to an aggressive 4-3 scheme, but he played in a similar attacking defense at Wisconsin.

The only other holdover from last season's 53-man roster is Destiny Vaeao. The undrafted rookie played in all 16 games and tallied 19 tackles, two sacks, three hurries, and a forced fumble playing 26 percent of the snaps. The Eagles also signed rookie Aziz Shittu off the practice squad and picked up journeyman Justin Hamilton this offseason.

With Taylor Hart's move to the offensive line, they will need to add more depth. The draft could provide, and maybe the Eagles find a starting-caliber defensive tackle in the early rounds. But with Logan's expected departure, there aren't any easy answers when it comes to his replacement.