Michigan Wolverines quarterback Wilton Speight likely is out for the season with a back injury.
Speight has three broken vertebrae in his back, a source confirmed to ESPN on Sunday.
ESPN's Chris Fowler first reported Speight's injury just before Saturday night's kickoff of Michigan State's 14-10 upset of No. 7 Michigan in Ann Arbor, telling viewers: "He is out, probably for the season. He has three broken vertebrae, he told us."
Speight, a fourth-year junior, was injured during the first quarter of Michigan's Sept. 23 win over Purdue with an undisclosed injury. He was hit awkwardly by a defender while on the ground.
Although Speight likely will be out for the rest of the season, he will be re-evaluated six to eight weeks after the injury happened, according to ESPN.
Head coach Jim Harbaugh declined to elaborate when he was asked earlier in the week about the nature of Speight's injury.
"I think you can talk to Wilton about that, or the doctors," Harbaugh said. "He's going to be out."
Speight was on the field Saturday at Michigan Stadium prior to the game against Michigan State.
Speight completed 54.3 percent of his passes this season for 581 yards, three touchdowns and two interceptions before the injury. He was replaced by backup John O'Korn, who helped the Wolverines rally to a 28-10 win against Purdue.
O'Korn started against Michigan State, going 16-of-35 passing for 198 yards with three interceptions as Michigan (4-1) lost its first game.