(John McDonnell/The Washington Post)

RICHMOND – Although lost for at least three months – and possibly longer – because of a torn left pectoral muscle suffered Thursday, second-year linebacker Keenan Robinson has been a constant on the Redskins’ sidelines during practice and in their meeting rooms on Friday.

Robinson is expected to have surgery to repair the muscle in a week or two when orthopedic surgeon James Andrews returns from a trip outside the country. But until then, Robinson intends to approach training camp as he would if he were healthy.

He is attending all of his unit and positional meetings for what accounts to roughly four hours of classroom time a day, studies the playbook on his iPad during his downtime and watches every practice, taking mental reps, as Coach Mike Shanahan calls it.

“As bad as I want to be out there, I can’t right now,” Robinson said on Saturday. “So, the next best thing I can do is try to learn, mentally. I’ve developed over the last year, the mental aspect of my game, and I was ready to apply that to the field, but I got hurt again, and so I’ll have to do it again. Hopefully next year I’ll be even better than I am this year.”

Robinson missed five games with a torn right pectoral muscle last season. That injury occurred while trying to make an arm tackle on Thanksgiving against Dallas. This latest injury occurred when Robinson lost his balance during a play in Thursday’s practice and reached down to brace himself.

“It was a freak accident. The way I came down on it and braced myself, it was awkward,” Robinson said, speaking extensively on the injury for the first time. “How it happened, who knows? It might not have been preventable.”

Robinson saw this year as an opportunity to develop on the field in a relief role and prove to coaches that he is capable of taking over for London Fletcher at the “mike” inside linebacker spot should Fletcher, 38, who is in the final year of his contract, decide not to return.

“As far as development goes, mental reps will only take you so far,” Robinson said. “You need on-field reps, and that’s what I’m missing right now. … I could’ve been that guy to give [Fletcher] that break, and me not being able to do that, someone else has to step up. I think this will hinder my development, but I can take the positives and try to improve my mental advancement of the game and try to learn from this.”

Robinson said that he isn’t closing the door on a return during the 2013 season. The Redskins believe he will need at least three to five months to recover. But the exact damage of his injury isn’t yet known. Fluid in the area made the results of his MRI exam difficult to read, Robinson said. Andrews will learn the full extent of the damage when he performs the surgery, and then the timeline for recovery could be revised.

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

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What’s ahead:

Saturday’s second practice is at 3:20. Here’s our guide to camp, if you’re going. There is no practice on Sunday.

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