"As soon as I got hit I screamed," he said. "It hurt really bad."
Despite the scene on the field moments after RG3 sustained the blow to his knee, Redskins spokesman Tony Wyllie told reporters Sunday that Griffin underwent an MRI and has a sprained right knee but that "everything is clear" in terms of significant ligament damage. Wyllie specifically ruled out a season-ending torn ACL, according to ESPN.
Griffin left for one play, then returned for four more, completing two passes to get the Redskins deep into Ravens territory. Hopping on one leg, Griffin eventually fell to the turf and could no longer continue.
"I knew I needed to get out at that point," Griffin told reporters. "I couldn't move. At some point you have to do what's right for the team. And if I'm playing the rest of that game, I probably would have hurt myself even more."
The 2011 Heisman Trophy recipient was replaced by back-up quarterback Kirk Cousins who entered the game with the Redskins trailing 28-20.
Cousins saved the day with an 11-yard touchdown strike to Pierre Garcon with 29 seconds left in regulation. He then ran for the two-point conversion to force overtime.
The Redskins eventually claimed a 31-28 victory over the Ravens with a 34-yard field goal by Kai Forbath four minutes into the extra session.
"We're happy that we won, obviously," left tackle Trent Williams told reporters after the game. "But that is concerning, knowing he went down. Everyone wants to know how he's doing."
Following the game, Griffin underwent an X-ray at the stadium, and according to the first round draft pick, doctors poking at his knee told him that his ligaments "felt good."
"I'm not a doctor, but I know what an ACL feels like," Griffin said. "And it doesn't feel like an ACL. ... If I felt that, I'd be pretty nervous. But we won the game, everybody's praying for me, I feel pretty good right now about the whole situation. I'm not too nervous, but I'll definitely be praying during the MRI."
When Griffin departed, he was 15 for 26 for 246 yards and a touchdown pass. He also ran seven times for 34 yards.
This is the second time this season that the No. 2 overall draft pick has been unable to finish because of an injury. He left the Oct. 7 loss to the Atlanta Falcons because of a concussion, but returned the following week.