ANN ARBOR, Mich. — Michigan found out just how valuable quarterback Wilton Speight is the hard way.

De'Veon Smith ran for two touchdowns in a 3:33 span late in the third quarter, finishing with a career-high 158 yards rushing, to help the fourth-ranked Wolverines shake off Indiana with a 20-10 win Saturday.

John O'Korn made his first start for Michigan (10-1, 7-1, No. 3 CFP), replacing its injured starting quarterback, and struggled to lead an offense that was averaging 45 points and 232 yards passing.

“Luckily, our run game and our O-line had my back,” O'Korn said.

O'Korn was 7 of 16 for just 59 yards.

“I'm not real pleased with the way I threw the ball, but that's part of battling the elements,” O'Korn said on a blustery day that left the field covered in snow in the fourth quarter.

O'Korn's best play was a 30-yard run, escaping a collapsed pocket on third down to set up Smith's shifty 34-yard run that put the Wolverines up 13-10 with 4:02 left in the third. Smith's 39-yard run later in the quarter put them ahead 20-10.

“That was huge,” Michigan coach Jim Harbaugh said. “We were struggling, making third-down conversions. And there was not just one, but two defenders pressuring John.”

For two-plus quarters, it looked like the Hoosiers (5-6, 3-5) might win one of the most significant games in school history. Indiana has beaten only one top-five team, No. 3 Purdue in 1967, the last year it won at Michigan Stadium. The Hoosiers haven't knocked off a top-10 team since beating No. 9 Ohio State in 1987.

Indiana's Richard Lagow was 14 of 29 for 191 yards, and Devine Redding was held to 50 yards rushing on 22 carries a week after running for 108 yards and two touchdowns in a loss to then-No. 12 Penn State.

“Offense did some things they needed to against a great defense,” Indiana coach Kevin Wilson said. “Just wasn't good enough.”

Still, the Hoosiers have been good enough to be competitive with ranked teams this season. That's a sign of improvement. If Indiana avoids getting upset by rival Purdue at home, it will earn consecutive bowl bids for the first time since 1990 and 1991.