Jim Tomsula got a little more help for his defensive line. (John McDonnell / The Washington Post)

It wasn’t long ago that one of the bright spots for the Washington Redskins was their defensive front, especially against the passing game. But now seven games into the season, it’s just another question mark, another unit decimated by injuries.

Washington heads to Seattle and will be without defensive lineman Matt Ioannidis, who had surgery to repair a fracture in his hand. It’s the second big loss the line has suffered in recent weeks, as they were already forced to shuffle personnel to account for Jonathan Allen’s season-ending foot injury.

The Redskins still plan to rotate five defensive linemen Sunday against the Seahawks and added veteran Arthur Jones on Wednesday for help. The eighth-year lineman took the roster spot of safety Stefan McClure, who was placed on injured reserve, and practiced for the first time Wednesday afternoon with his new teammates. Redskins Coach Jay Gruden said he’s hopeful Jones “can slide right in.”

“He’s a fast learner,” Gruden said. “Talking to him out there, he’s already got a good grasp of the game. Now it’s a matter of what kind of shape is he in, and I think he’s down some pounds, so he looks pretty good. But over the course of five-, six-, eight-play drives, we’ll see how he does.”

Jones, a fifth-round draft pick by Baltimore in 2010, started eight games for the Indianapolis Colts last year and was released in March. He said after Wednesday’s practice that despite the long layoff, the transition has been a smooth one and his familiarity with Washington defensive coordinator Greg Manusky has been helpful. Jones played under the Redskins’ coach when Manusky was the defensive coordinator in Indianapolis.

“It’s very similar playbook-wise,” Jones said of the Redskins’ scheme. “I just love playing for the guy. He’s a passionate guy, a guy who loves the game, a guy who played the game for many years. I’m happy to reunite with him. So many great guys on this defense. I’m excited for whatever role they give me to play and try to earn these guys’ respect.”

Gruden wasn’t sure when Ioannidis might be healthy enough to play. He’s hopeful the second-year lineman will be able to compete wearing a cast in the next couple of weeks, and the Redskins can continue to be effective up front.

“I think our front, when we were healthy, we had Ziggy [Hood] and Jonathan Allen and Matt, and we had a good rotation with Stacy [McGee] and Terrell McClain,” Gruden said Wednesday. “Now, with Matt and Jonathan out, our guys are going to have to step up. Stacy is going to have to play more, Terrell is going to have to play more, and now we have Arthur Jones in the mix, and obviously Anthony Lanier … but I think we just have to get those guys, taking Jonathan and Matt’s spot, to step up and play their gaps.”

Since losing Allen in the Redskins’ Week 6 win against the 49ers, the Redskins’ defense has slipped statistically, as Washington lost back-to-back games against division foes Philadelphia and Dallas.

The Redskins had the league’s eighth-best run defense through Week 6, which fell to No. 13 after last Sunday’s loss against Dallas. The Eagles posted 371 total yards against a defense that had been allowing an average of 316 entering the game. The next week Cowboys running back Ezekiel Elliott hung 150 rushing yards on the Redskins, the most they’d allowed this season.

Allen, the Redskins’ first-round draft pick, suffered a Lisfranc sprain in the second half of the team’s Week 6 win over the San Francisco 49ers, prematurely ending his rookie campaign.

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