ANN ARBOR, Mich. — John O'Korn has his first chance to take extended snaps at Michigan.

O'Korn will get the start for the seventh-ranked Wolverines against Michigan State on Saturday night because injured quarterback Wilton Speight is out indefinitely with an undisclosed injury.

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Harbaugh has not revealed details of the injury to Speight, who was hurt in the first quarter of a Sept. 23 victory at Purdue. Speight left the stadium for X-rays and Harbaugh later referred to it as a "soft tissue" injury.

"He won't be able to compete this week or for multiple weeks," Harbaugh said Monday.

Speight was relatively shaky in three-plus games this season after he was a solid starter in 11 games last year, earning third-team All-Big Ten honors. The senior completed just 54 percent of his passes this season for 581 yards with three touchdowns and two interceptions, both of which were returned for scores in the season-opening win over then-No. 17 Florida. He connected on 62 percent of his throws last year, winning his first nine games, with 18 TDs and seven interceptions.

O'Korn started one game last season against Indiana in place of Speight, who hurt his shoulder in the previous game. He will likely face a stiffer test when the Wolverines (4-0, 1-0 Big Ten) play the rival Spartans (3-1, 1-0) at home.

The fifth-year senior began his career at Houston, where he started 16 games and threw 34 touchdowns over his freshman and sophomore seasons. He then transferred to Michigan and finished second to Speight in a competition to be the team's No. 1 quarterback last season and again this year. Instead of starting, as O'Korn hoped he would when he left the Cougars, he spent a lot of time standing on the sideline during games.

"He's done a great job of handling it, on and off the field, and he stayed patient," fullback Khalid Hill said. "He understands his time could come at anytime. Coach (Harbaugh) is always preaching, 'Next man up,' and O'Korn prepares like it. That's why he was ready to come out and play Purdue like he did."

O'Korn was 18-of-26 for 270 yards with a touchdown and an interception in last month's 28-10 win over the Boilermakers.

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"John's done a fantastic job ever since he got here in every role that he's been in," Harbaugh said. "He's acquitted himself well, including coming off the bench and leading our team to victory against Purdue. I think that speaks volumes."

Harbaugh had a lot to say last week about the hit that Speight took from Boilermakers defensive tackle Eddy Wilson in the back of the head and neck area after linebacker Markus Bailey had already taken him to the ground with a sack.

"I thought it was egregious," Harbaugh said two days after the Purdue game. "If I had a stronger word to use, I'd use it. With all the emphasis on protecting defenseless players, it appeared the player knew what he was doing, targeted the head and neck area when the player was on the ground and accelerated into it."

No penalty was called on the play that knocked Speight out of the game.