IRVING, Texas — The next man up for the depleted Dallas defense is Batman. That’s the way newcomer Brady Poppinga is looking at it, anyway.

Poppinga joined the Cowboys on Monday as the roster replacement for linebacker Bruce Carter, who will miss the rest of the season with a dislocated left elbow. Carter is the fourth starting Dallas defender to be placed on injured reserve.

A seven-year veteran caught up in a mess of defensive injuries when Green Bay won the Super Bowl two years ago, Poppinga last played in the 2011 season finale for St. Louis on New Year’s Day. He’s been working out and waiting for another chance ever since.

“I was in what you call Batman shape, meaning when I get the call, boom, I put the mask on, I’m gone,” Poppinga said. “I got the mask on, so here I am.”

Problem is, the Cowboys may need Superman and a few of his friends to help a defense missing a third of its starting lineup and two key reserves. It comes off a demoralizing second quarter that put Dallas in a 28-3 hole on the way to a 38-31 Thanksgiving loss to Washington.

Dallas is now without both starting inside linebackers in Carter, injured in the third quarter against the Redskins, and defensive leader Sean Lee, who badly injured a toe last month.

Dan Connor, an offseason free agent pickup from Carolina, will be the third defensive play caller at the start of a game Sunday against Philadelphia. The player next to him will likely be Ernie Sims, signed off the street a month ago after Lee was injured. Poppinga could be the primary backup.

“The next man up philosophy is alive and well with the Cowboys,” Dallas coach Jason Garrett said. “Always has been, so if you’re a part of the 53-man roster, you’d better be ready to play.”

Several Dallas defenders apparently weren’t ready when the second quarter started Thursday against Washington. Robert III Griffin, the Heisman Trophy winner from Baylor, was 8 of 8 for 178 yards with three touchdowns in Washington’s first four-touchdown quarter in 13 years. Another rookie, Alfred Morris, averaged 7 yards per carry and had the other touchdown. The Redskins only faced two third downs, and converted both.

“They hit some big plays and we weren’t playing very well,” Dallas defensive coordinator Rob Ryan said. “That’s just the truth.”

The defense helped the Cowboys get back in the game, even getting just the fourth interception of Griffin this season to set up a touchdown that made it a seven-point game with plenty of time left. But then Ryan’s bunch let down again, allowing the Redskins to run nearly 5 1/2 minutes on a field goal drive that killed any realistic hopes of completing the rally.

Dallas had a similar letdown five days earlier when a great defensive stand was followed on the next Cleveland possession by a communication problem., That gave the Browns a go-ahead touchdown in the final minutes before the Cowboys came back and won in overtime.

“That’s something we really focused on last year coming into this year is just not giving up those big plays and communication and all that stuff,” said linebacker Anthony Spencer, who has a career-high 6 1-2 sacks after taking down Griffin twice. “We just had a few of those things happen in this game that we definitely can’t have happen.”

Carter wasn’t the only Dallas defender who didn’t finish the Washington game. Defensive end Jason Hatcher, a key replacement with Kenyon Coleman gone for good with a torn triceps, had to leave with a concussion. Orlando Scandrick, the extra cornerback in pass coverage in a secondary already missing safety Barry Church (torn Achilles tendon) for the season, injured his left hand and is out indefinitely after surgery.

“Those are three ... good guys to add to the list of about a hundred, but that’s the way it is,” Ryan said. “We’ll get back.”

Cornerback Morris Claiborne said Ryan’s message hadn’t changed Monday.

“His mood and mindset don’t really change,” Claiborne said. “He still feels like we’re the best team in this league no matter what and he’s the best coach. So his spirit will never change.”

NOTES: Dallas released WR Andre Holmes and replaced him with veteran Anthony Armstrong after Miles Austin injured a hip in the Washington game. ... The Cowboys signed CB Reggie Jones to the practice squad to replace WR Danny Coale (hamstring), who was placed on injured reserve.

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