Defensive lineman Adam Carriker lays on the field after being injured, and subsequently lost for the season, in Week 2 of 2012. (Tom Gannam/Associated Press)

RICHMOND — Defensive end Adam Carriker had surgery on his problematic right quadriceps tendon and is expected to need four to five months to recover, Redskins Coach Mike Shanahan said.

It marked the third surgery that Carriker has had on the tendon since tearing it early in the second game of last season. Carriker hoped to return to action this season, but had to have a second surgery earlier this year and was expected to open training camp on the Physically Unable to Perform list.

The leg still hadn’t healed properly and a third surgery was required.

Shanahan said, “He had the couple surgeries. I’m not exactly sure what happened, but any time you do have a surgery – and you take a look at the progression of the knee and the quad, it just was not producing to where he could get the movement in his legs that would give him a chance to play. He could work with the weights, but he just couldn’t get the circulation, couldn’t get the movement, and that’s basically why he’s had three surgeries. Hopefully this surgery will give him the ability to have that type of movement that he needs as a defensive lineman to get in that stance and have that explosion.”

Carriker, 29, said in a text message Wednesday night that he is determined to return to the football field. Shanahan said although it looks bleak, a return this season hasn’t been ruled out entirely.

“You know, there’s always a chance for it to happen before. I just don’t know,” the coach said. “But according to the doctors, the surgery was something that he needed. It went as well as they possibly could have hoped for. That’s always a good sign.”

Meanwhile, second-year linebacker Keenan Robinson suffered an injury to what appeared to be his left shoulder area in Thursday afternoon’s practice and had to have an MRI exam. Robinson missed a portion of last season with a torn right pectoral muscle.

The Redskins on Thursday afternoon activated Josh Wilson from the PUP list, ending what the cornerback jokingly called the record for the shortest stint under that designation.

Wilson was rehabbing from surgery on the labrum in his left shoulder, and the Redskins wanted to further evaluate his strength, and thus put him on the PUP list at the start of camp. After the morning walk-through, Wilson was taken into the weight room where he lifted for the team’s medical staff. Pleased with his performance, they activated him.

Wilson did only individual drills in Thursday’s practice.

Have a Redskins question? E-mail Mike Jones at with the subject line “Mailbag question” for him to answer it in The Mailbag.

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What’s ahead:

The team will practice on Friday at 10 a.m. and 3:20 p.m.

We’ll post Mike Jones’s Day 1 observations first thing in the morning.

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