INDIANAPOLIS (AP) – Jared Sullinger had 20 points and 18 rebounds as No. 1 Ohio State barely avoided a stunning upset, beating Northwestern 67-61 in overtime Friday in the Big Ten tournament quarterfinals.

Sullinger made all 10 of his free throws in overtime after missing a baseline jumper that would have won the game as time expired in regulation. His 18 rebounds fell one short of the tournament record set by Ohio State’s Greg Oden in 2007.

Top-seeded Ohio State, the defending tournament champion, won its fifth straight game to advance to Saturday’s semifinals.

The Buckeyes led 56-55 in overtime when Luka Mirkovic was called for hooking Sullinger while they fought for a rebound. Mirkovic was issued a technical foul for arguing about the call. It was his fifth foul, and Sullinger’s primary defender was gone.

William Buford missed both technical free throws, but Sullinger made his two foul shots to give Ohio State a 58-55 lead. The Buckeyes maintained control by going 6 for 6 from the free throw line the rest of the way.

Aaron Craft scored 17 points and Jon Diebler added 13 for the Buckeyes (30-2).

John Shurna scored 23 points, Michael Thompson added 15 and Drew Crawford had 12 points and 10 rebounds for the eighth-seeded Wildcats (18-13). Thompson was coming off a tournament-record 35 points in Thursday’s win over Minnesota.

Ohio State shot 32.2 percent from the field, matching its worst effort of the season, but outrebounded the Wildcats 48-27.

The teams battled back and forth in the second half until the final minute. With the score tied at 52, Northwestern had a chance to take the lead, but David Lighty blocked Crawford’s jumper. Then Sullinger’s shot fell short as time expired.

Shurna’s shooting kept Northwestern in the game early in the second half, and Thompson’s short jumper with 10:54 remaining gave Northwestern a 38-37 lead.

Ohio State couldn’t hit early, and Northwestern took advantage. Shurna made a 3-pointer to give the Wildcats a 16-14 lead with just under 7 minutes left in the first half.

The Buckeyes missed 21 of their first 31 shots, but Craft hit a 3-pointer, then a layup to give the Buckeyes a 26-23 lead in the final minute of the first half. After frantic action near the basket, Craft’s tip-in at the buzzer gave the Buckeyes a 28-23 lead at the break.