Jared Sullinger had a rough day shooting from the floor but nailed all 10 of his free throws in overtime as No.1 Ohio State survived a scare from Northwestern, 67-61, in a Big Ten quarterfinal matchup Friday.

Sullinger shot just 2 of 12 from the floor, but his size was too much to overcome on the low box, as the Buckeyes (30-2) repeatedly fed the burly power forward down the stretch. The Big Ten Freshman of the Year converted 16-of-18 free throws overall, and the Buckeyes advanced to Saturday’s semifinal against the Michigan-Illinois winner.

Sullinger hit six free throws and sharpshooter Jon Diebler hit his only 3-pointer with 2:22 left in overtime to give Ohio State a 61-55 edge with 2:22 left. Sullinger hit four more shots from the charity stripe to close it out. He finished with 20 points and 18 rebounds. Aaron Craft added 17 points and seven rebounds.

John Shurna scored 23 points to lead the Wildcats (18-13), and Michael Thompson, who scored a career-high 35 against Minnesota on Thursday, added 15.

Ohio State closed the first half on a 9-0 run to forge a 28-23 lead. Five points would also be its biggest lead of the second half. Northwestern’s biggest lead was 49-46 with 4:48 remaining in regulation.