On Monday night, Flacco was hit by the helmet of Detroit Lions linebacker DeAndre Levy, who had dived at the reigning Super Bowl MVP midway through the fourth quarter of Baltimore's 18-16 win. An MRI revealed a mild MCL sprain, a league source told ESPN NFL Insider Adam Schefter.
Flacco didn't have a noticeable limp when walking to the practice field and to the locker room. He wore the brace in Wednesday's practice and will wear it against the Patriots, whether the trainers recommend it or not.
The only time Flacco has worn a brace was his junior year at Delaware, where he sprained the MCL in the same knee.
"It was uncomfortable a little bit," Flacco said of the brace. "If it protects it, it's all good for me."
Flacco acknowledged the knee was stiff the past few days and believes the swelling will go down. According to Flacco, the injury only needs rest and won't require surgery in the offseason.
"It's getting better, that's a good sign I think," he said.
When he initially took the hit, Flacco and the rest of the Ravens were concerned. Flacco has taken hard shots in the past, but this was considered the most dangerous.
"I remember a few shots that he's taken lower body and to the knee," Harbaugh said. "I don't remember him taking one that bad."
Flacco said it was a scary feeling when the helmet collided with his knee.
"I felt something obviously when I got hit down there," Flacco said. "And then Ray came over and wanted me to get up but he didn't really help me. I wasn't really ready to get up yet because I didn't want to get up and test it out and have myself collapse to the ground and look like a hit. Yeah, it was little scary. I've never really had a severe knee injury, so you don't know what is what. So when you feel something, you definitely get a little bit scared."
Flacco was able to put pressure on his left knee when he got up and didn't miss a snap the rest of the game.
"My mind was at ease as soon as I got up," Flacco said.
Flacco was upset that the hit, which falls under the "Brady Rule," didn't draw a flag. Harbaugh said he got a different explanation from the referee on the field Monday and the league office Wednesday morning.
"They're going to send it up for discipline and we'll just have to see what the league does for it," Harbaugh said.
"That's one of the first things you think about when you get hit there and you go down, you're like, 'Shoot, I'd better not be able to not be able to play,'" Flacco said. "Definitely, very proud of that. Hey, listen, at some point, it may happen that I can't go out there and start a football game. We're going to try to hold that off for a while."