An MRI done Sunday revealed that Griffin has "an isolated tear" in his ACL. He sustained the injury in the first half of the Bears' 68-13 victory over Northwestern State on Saturday night.
The Bears also lost senior defensive back and return specialist Mikail Baker to a knee injury. An MRI revealed an ACL tear and tears to his medial and lateral meniscus after he was hurt on special teams.
Griffin was injured when his leg bent awkwardly while being stopped for no gain on a fourth-down play the opening series of the game. He remained on the ground for several minutes, the silence broken only when Baylor students started chanting his name before he walked gingerly to the sideline.
Northwestern State drove for a touchdown and a 7-0 lead while Griffin was being tended to. He had his knee heavily wrapped, but didn't miss a snap before halftime and led the Bears to a 41-10 lead. Griffin was 13-of-19 passing for 226 yards with three TDs before watching the second half from the sideline.
Baylor coach Art Briles didn't return a message from The Associated Press left on his cell phone Sunday night. School officials said they didn't expect to have any comments from the coach or Griffin.
When asked after Saturday night's game to rate on a scale of 1-to-10 his level of concern when Griffin remained on the ground, Briles responded, "We're stopping at 10? ... I like winning football games."
Just moments earlier, Griffin had limped away from the podium after saying he wasn't concerned.
"I played on it, so I should be able to play on it again," Griffin said after the game.
During his Sunday teleconference before the MRI had been done, Briles expressed hope that it was not "anything major" and said he was encouraged that Griffin had been able to finish the first half Saturday night.
Griffin accounted for 28 TDs (15 passing, 13 rushing) as an 18-year-old freshman last year. With him back for a second season, the Bears came in hoping for their first bowl since 1994. The 15-year drought matches Duke for the longest for a team playing in a Football Bowl Subdivision conference.
Blake Szymanski, a senior who was a starter before Griffin arrived on campus, took over after halftime against the Demons and was 3-of-5 for 58 yards and a touchdown. But he bruised his right shoulder when he was hit on a rush near the goal line.
Baylor's training staff listed Szymanski, who had X-rays Sunday, as day to day.
Tailback Jay Finley, who missed Saturday's game with a sprained ankle, is probable for the Bears when they play their final non-conference game Saturday at home against Kent State.
The Big 12 opener is Oct. 10 at eighth-ranked Oklahoma.