McClain will be placed on injured reserve due to a spinal cord concussion after getting a second opinion from a California specialist that confirmed the initial diagnosis.
McClain won't need to undergo surgery, though, and is expected to make a full recovery in time for next season.
"He will be done for the season on that," Ravens coach John Harbaugh said. "That will not have time to heal before the end of the season."
Signed to a $10.5 million contract in March, McClain got hurt during a 31-28 overtime loss to the Washington Redskins. He finished the season with 78 tackles and three pass deflections in 13 starts.
McClain will become the 11th Baltimore player to be placed on season-ending injured reserve.
No immediate roster move was made for McClain, but have a few options available. They could activate middle linebacker Ray Lewis (torn right triceps) from the injured reserve-designated to return list or promote one of their two practice-squad linebackers: Nigel Carr or Adrian Hamilton.
Meanwhile, Harbaugh was noncommittal on the potential return of offensive guard Marshal Yanda (sprained right ankle), strong safety Bernard Pollard (rib contusion) and tight end Ed Dickson (hyperextended knee).
"We’ll see as the week goes on how those guys progress from those things," Harbaugh said. "Obviously, those things are unpredictable."
Cornerback Jimmy Smith returned on a part-time basis after missing five games following sports hernia surgery, but allowed a catch that set up a touchdown run. Operating in the nickel package, the 2011 first-round draft pick's movement wasn't entirely back to normal.
"He wasn’t 100 percent out there, and that’s something you really don’t know until you get into the game," Harbaugh said. "Unfortunately, he wasn’t as quick as I would have hoped he would be.. Sometimes in practice, it’s a little harder to judge that.”