Hall said Sunday night that doctors told him it likely was his ACL. A team source and Hall's agent Alvin Keels confirmed the newsto ESPN.
"He's coming along, playing better and better at safety, so it's pretty significant," Redskins coach Jay Gruden said Monday. "From a player perspective, Will's right there with him, but from a leadership standpoint, D-Hall has done a lot for this organization, a lot for this team. He's going to be missed."
Hall hurt his knee in the second quarter of Sunday's 29-27 win over the New York Giants when he was making a tackle attempt on receiver Odell Beckham Jr. The Redskins have another former corner,Will Blackmon, and Duke Ihenacho as backup safeties.
For Hall, it's the third straight injury-shortened season. He played in only three games in 2014 thanks to an Achilles tear and was limited to 11 games last season as he recovered from that injury and also dealt with a knee issue. He turns 33 in November, which might have made Sunday's game his last with Washington.
"He's got to really take a look at it and see where he is once he does the rehab, if he wants to try it again," Gruden said. "I haven't talked to him about that. We just want him to get well first. That's the No. 1 priority right now."
On Saturday night, Hall organized a team meeting.
"I didn't feel guys were out there having fun," Hall said. "I told them at any given moment you never know when your last snap is going to be. That could have been my last snap. It's [crushing], but that's football."
He wasn't the only Redskins defensive back to be hurt Sunday. Corner Bashaud Breeland suffered a high right ankle sprain in the first quarter; he left the stadium in a walking boot and on crutches and was undergoing an MRI Monday as well.
The Redskins also lost two offensive line starters to injuries in the game -- guard Shawn Lauvao (ankle) and center Kory Lichtensteiger (calf) -- forcing Pro Bowl tackle Trent Williams to play most of the second half at left guard.