With 2:05 left in the first quarter, McNair suffered a medium concussion and medium neck sprain after avoiding hard-rushing Panthers defensive tackle Kris Jenkins and being sacked by linebacker Chris Draft and defensive end Mike Rucker.
The Ravens aren't exactly sure how serious McNair is hurt, but it doesn't appear to be too bad.
With a bye week to rest, there is a decent chance McNair will be back as the starting quarterback when the Ravens visit the Saints Oct. 22.
McNair was immediately taken off the field and eventually rushed to Union Memorial Hospital. Initial X-rays at the stadium were negative, but the team wanted to be sure. He was taken to the hospital for a CT scan of his neck and an MRI of his head. He also suffered an abrasion of the neck.
After a couple of hours, McNair was released from the hospital.
"I don't know," Ravens coach Brian Billick said of McNair's condition. "I'll leave that to the doctor. The last word I had was they went in to get some imaging. He definitely had the concussion and wasn't able to come back in."
Kyle Boller finished the game and completed 17 of 31 for 226 yards and three touchdowns. He also had an interception and a fumble.
"It's tough," Billick said. "With any backup quarterback the amount of reps you take during the week, you don't get substantial reps. And then you have to go in and execute the game plan. So for any level of productivity, that's a positive thing. We'll go in and look at the film. We'll look it at very critically. I know he's excited about getting the opportunity to contribute to this team."
Said Ravens receiver Derrick Mason, "Hopefully, it wasn't that serious where Steve will miss any time. It's kind of good that the week off will help him. Kyle came in and did an excellent job. He came in on short notice. He did an excellent job."
John Clayton is a senior NFL writer for ESPN.com.