Because teams can return two players off injured reserve, the Redskins won't rule Allen out for the season, multiple sources told ESPN.
One source told ESPN this is a "just in case" scenario and the team doesn't want to close the door on a possible return before seeing Allen's progress after eight weeks. He had surgery Wednesday, and there is at least some level of optimism that he could return, multiple sources said.
Coach Jay Gruden said the outlook for Allen changed Wednesday night after he underwent surgery.
"We got better news after the surgery that it wouldn't be as lengthy as they typically are," Gruden said. "That's good news. But we still have to rehab it. He's a big man and sometimes bigger guys take a little bit longer. We'll wait and see. Hopefully we see him again, but it's up to the rehab."
Redskins tackle Morgan Moses underwent the same procedure at the end of the 2014 season and was told to apply no pressure to his foot for six to eight weeks.
The Redskins already have kicker Dustin Hopkins (hip) on injured reserve, and he might be able to return after eight weeks, if needed. Considering the Redskins (3-2) don't have anyone else yet on injured reserve who is eligible to return -- and where they're at in the season -- it makes sense to hold out hope for a comeback.
Regardless, Allen's extended loss is a blow to the defensive line. Though he only has one sack, he and Matt Ioannidis have paired to provide an effective pass-rush push in the middle of the line, leaving quarterbacks with less room to escape and the edge rushers with more chances for sacks.
"That's a big loss," cornerback Josh Norman said. "I won't sit up here and say it isn't. It is a big loss for us. He's one of our driving forces in the middle. He creates havoc on the field. It goes without saying that to not have him for a while like that is pretty big."
The Redskins selected Allen with the 17th pick of the draft in April.