Quarterback Kirk Cousins was benched in the second half, and backup Colt McCoy helped the Redskins to a comeback victory over the Titans, 19-17. The Washington Post's Gene Wang and Dan Steinberg break down the game and who might be the starting quarterback in Week 8 against Dallas. (Meghan Sims/The Washington Post)

The Washington Redskins on Monday experienced another setback when an MRI exam revealed outside linebacker Brian Orakpo will miss the remainder of the season with a torn right pectoral muscle. The sixth-year veteran soon will have surgery to repair the tear, Coach Jay Gruden said.

Gruden called the second season-ending injury to a defensive starter this season a “blow.” In Week 3, cornerback DeAngelo Hall ruptured his left Achilles’ tendon. Now, Orakpo will join him on the injured reserve list.

The injury ends a disappointing season for Orakpo, while forcing team officials and coaches to scramble for alternatives to shore up an already-anemic pass rush.

“It’s a blow,” Gruden said. “DeAngelo was a blow obviously to the secondary, you lose a proven starter like that and have to play the people behind them, and it hurts your depth and hurts your leadership, obviously. It’s the same thing with Brian.

“I know his production may not be where people think it should be,” Gruden added, referring to the half sack that Orakpo recorded in seven games. “But he's still been playing very good against the run and disruptive in the passing game, and it'll be a blow.”

Orakpo had not lived up to his three-time Pro Bowl status or the $11.455 million investment Washington made in him for this season. After recording a team-high 10 sacks in 2013, Orakpo’s contract expired, and he sought a long-term deal from the team that drafted him 13th overall in 2009.

But the two sides couldn’t come to an agreement, and Washington retained his services by using the franchise tag on him.

Orakpo didn’t come close to the production Washington had hoped for.

He recorded a hit on the quarterback Sunday against Tennessee, but for a fifth consecutive week went without a sack. Orakpo left the game on the second play of the fourth quarter with what was originally described as a right shoulder injury.

After the game, Gruden said the injury actually was to Orakpo’s right pectoral and described the damage as significant. Monday’s MRI revealed the extent. It’s the third such injury that Orakpo has suffered. At the end of the 2011 season he tore the left pectoral muscle and then tore the same muscle two games into the 2012 campaign.

Two hours after news broke of Orakpo’s test results, the linebacker tweeted, “Redskin Nation I’m truly sorry for this injury plagued season I went thru. Thank u all for the love and also the criticism that will only make me stronger when I return. Thanks for all the support and let’s smash them Cowboys Monday Night! #HTTR”

Orakpo’s injury thrusts rookie Trent Murphy into a starting role. The Redskins had previously used the second-round pick out of Stanford to spell Orakpo or fellow outside linebacker Ryan Kerrigan, who leads the team with 61 / 2 sacks.

“I know his production may not be where people think it should be,” Coach Jay Gruden said, referring to the half sack Brian Orakpo recorded in seven games. “But he's still been playing very good against the run and disruptive in the passing game, and it'll be a blow.” (Ricky Carioti/The Washington Post)

Murphy, who last year led the NCAA in sacks, also occasionally joined the two veterans in nickel packages.

“He’s got to step up his game,” Gruden said. “He has got to play better. He has got to play more physical at the point of attack. We are playing against the number one rushing offense in the National Football League [in Dallas], so he is going to have to be very good at the point of attack and then obviously transition into pass rush against some very good tackles. So he is going to have his work cut out for him. He’s going to have to grow up very fast.”

The Redskins will use undrafted rookie Jackson Jeffcoat to relieve Kerrigan or Murphy. Gruden also left open the possibility that practice-squad linebacker Gabe Miller could be promoted to the 53-man roster.

Questions will continue to loom over Orakpo’s future, however. Members of the organization had reservations about giving him a long-term deal this offseason when he was coming off of a healthy season, so the uncertainty over making a hefty investment in a player with spotty production, plus a new injury, will only intensify.

“We'll have to evaluate that after the season where we are, how Trent does,” Gruden said. “Obviously, we like Brian, and he has done some great things for the franchise, and that's something that'll have to be addressed when the season is over and moving forward. Bruce Allen and myself and the personnel department and the coaches will all talk about that.”