ON THE GROWING list of things that Chip Kelly and Howie Roseman will be fretting about this offseason, the Eagles' offensive line certainly isn't as pressing a concern as cornerback or safety or quarterback or Marcus Smith.

But it is a concern nonetheless. That was underscored Saturday with a yet another uneven performance by the line in the Eagles' disappointing 27-24 loss to the Redskins.

A year ago at this time, the offensive line was one of the Eagles' greatest strengths. It was a dominating unit that helped LeSean McCoy run away with the league rushing title and afforded Nick Foles enough pocket security to lead the league in almost every pertinent passing category. The five starters didn't miss a single game.

That hasn't been the case this season. Including right tackle Lane Johnson's four-game PED suspension, the Eagles' linemen have missed 22 starts. Left guard Evan Mathis missed seven with a knee sprain. Right guard Todd Herremans has been on injured reserve since early November with a torn bicep. Center Jason Kelce missed four games after needing surgery to repair a sports hernia.

"Last year, we were certainly lucky in the injury category," Kelce said after the Eagles' third straight loss Saturday. "This year, we've certainly been a bit unlucky. It's the nature of the game. That's way it goes. Arizona has been really unhealthy and they still seem to be doing pretty well."

The Eagles have had four of their five starters back together for the last six games. The only one missing has been Herremans, who has been replaced by Andrew Gardner.

But offensive-line coach Jeff Stoutland's unit hasn't played nearly as well as it did last year. Jason Peters, a six-time Pro Bowler, probably is going to be in the Hall of Fame some day. But this has not been one of his better seasons.

That was evident on Saturday when he was beaten for a sack by Redskins linebacker Trevardo Williams, who was playing in only his second NFL game. Guy was on their practice squad 2 weeks ago.

Johnson gave up a costly first-quarter sack/fumble to linebacker Ryan Kerrigan that killed a drive and helped the Redskins take an early lead. He also was called for a hold against Kerrigan, one of 13 penalties against the Eagles in the loss.

"Jeff made a couple of adjustments up front," Chip Kelly said. "We got beat on a couple of twists. Just passing things off. I think he made a couple of good adjustments and things settled down a little bit.

"I think Lane did a better job of getting used to what Ryan was trying to do to him. He's a really dynamic pass-rusher. But I thought as the game went along, those guys did a good job."

Mathis was a first-team All-Pro last season. Kelce played at a Pro Bowl level. Neither has come close to matching last year's performances since returning from injury.

Kelly's offense is driven by the run game, and it hasn't been nearly as effective this season as it was last year. Some of that has to do with the fact that opposing defensive coordinators had an offseason to study Kelly's offense and come up with ways to defend his inside and outside zone runs.

Some has to do with McCoy's decision-making, which hasn't been nearly as good as it was a year ago. And more than some has to do with the line, which just hasn't blocked as well as it did last year.

Last year, McCoy averaging 4.97 yards per carry on first down and 5.68 on second down. This year, he is averaging just 4.45 on first down and his second-down average has plummeted to 3.54. Against the Redskins, he rushed for 9 yards on eight carries on second down.

Last year, the Eagles averaged a league-best 6.83 yards per play on first down. This year, they are 16th with a 5.57 average. Averaged 5.7 yards per first-down play against Washington.

McCoy had a league-best 47 runs of 10 yards or more last season. With one game left this year, he has just 31.

McCoy rushed for 88 yards on 22 carries Saturday, but had just 19 on nine carries in the second half. The Eagles were 1-for-3 in the red zone in the second half. McCoy had just 3 yards on four carries on those three red-zone possessions.

Trailing, 17-14, late in the third quarter, the Eagles had a third-and-1 at the Washington 28. The Eagles ran an outside zone play to the right. But Gardner failed to execute his block on defensive end Stephen Bowen, who stopped McCoy for no gain. The Eagles ended up getting nothing on the drive. Right after Bowen stuffed McCoy, Cody Parkey missed his second field goal attempt of the game, a 46-yarder.

On the Eagles' next possession, Gardner was called for a hold and Kelce was pancaked by Redskins defensive tackle Kedric Golston on a second-and-6 run by McCoy at the Washington 14 that resulted in a 2-yard loss.

On the Eagles' next possession, McCoy was stopped for no gain on first-and-goal at the Washington 8-yard line. The Eagles ended up settling for a field goal.

"I don't really think the [two] turnovers were as big a difference as the failed red-zone opportunities," Kelce said. "We had opportunities to put points on the board. And not only didn't we come away with touchdowns, but no points is even worse.

"We have to do a better job as an offense. We've been harping on this all year. Putting touchdowns on the board when we get down there. We failed to do that again today."

The Eagles have converted just 49.1 percent of their red-zone opportunities (27 of 55) into touchdowns. They went into Saturday's game ranked 25th in the league in red-zone offense.

But even last year, they only finished 18th (52.6 percent). And they had to convert nine of their last 12 red-zone opportunities in their last five games to climb that high.

Some people feel Kelly's zone run game is too finesse-oriented to be consistently successful in the red zone. The Eagles' linemen, including Mathis, have argued that there is no more physical play in football than the inside zone run.

"That's the play we hang our hat on," Mathis said. "Show me any kind of finesse on that play. That's smash-mouth football."

The Eagles' offensive line isn't getting any younger. While Kelce and Johnson both still are young, Mathis is 33 and will count $6.5 million against the cap in 2015. Peters will turn 33 in January and has an $8.5 million cap number in 2015.

Herremans, who has suffered season-ending injuries in two of the last three seasons that have caused him to miss 15 of the last 39 games, is 32 with a $5.2 million cap number next season.

If they can stay healthy and play at a level comparable to last season, that is money well spent. If they can't and play as inconsistently as they did this season, it's going to be a problem for a team that already has quite a few of them.

"It's been very frustrating," Mathis said. "The first half of the season, not being able to be out there with my guys. And this is where we are now.

"All the work we put in, all the expectations we have for ourselves, this is definitely a frustrating place to be."

Asked if the line's biological clock is ticking, Kelce, 27, said, "I don't really get into the timing of things or look at careers or anything like that. Anybody can go out there, and [on] one play, it's done.

"So I don't think you can ever look at it like you've got X amount of years left in your career. Every game you go out there and it could be your last one. You just try to play the best you can."

On Twitter: @Pdomo
Blog: eagletarian.com