CHICAGO (AP) _ With Ken Johnson on the bench, No. 24 Ohio State got that sinking feeling Friday night.

Johnson, a two-time Big Ten defensive player of the year and the league's career leader in blocked shots, had to sit with foul problems and Iowa made the most of his absence.

Glen Worley scored 18 points, and Iowa rallied from a 13-point deficit in the second half to stun the Buckeyes 75-66 in the quarterfinals of the Big Ten tournament.

Iowa (20-11) will face another big upset winner, Penn State, in an unlikely semifinal Saturday night. The Nittany Lions shocked No. 2 Michigan State 65-63 earlier Friday night at the United Center.

Dean Oliver added 16 points for Iowa, and Brian Brown led Ohio State with 18 in a foul-filled game that featured 31-of-45 free-throw shooting by the Hawkeyes and 27-of-39 by the Buckeyes.

Johnson played a total of 16 minutes, scoring 12 points, but he never did pick up his fifth foul.

The third-seeded Buckeyes (20-10) built a 33-22 halftime lead with Johnson playing just eight minutes after picking up two fouls.

Johnson got his third foul in the first 30 seconds of the second half, but the Buckeyes still had a 13-point lead.

Johnson returned to hit four free throws but was assessed his fourth with 12:23 left when he got tangled up with Duez Henderson under the basket. Still, Ohio State led 42-35.

Then, with Johnson forced back to the bench, the sixth-seeded Hawkeyes took off on a 17-5 run.

Worley scored inside, and Henderson converted on a break to make it 42-41 to the delight of a large contingent of screaming Iowa fans.

The Hawkeyes finally tied it on Oliver's 3-pointer with 8:50 to go and then took their first lead as Oliver hit a pair of free throws with 7:29 left to make it 47-45.

When Reggie Evans banged inside for a three-point play, the Hawkeyes had a 53-47 lead. Johnson returned with 5:22 to go.

Evans went right at Johnson for an inside basket and then Henderson sank a 3-pointer to give the Hawkeyes a 58-48 lead.

Iowa put the game away by hitting 14 free throws in the final three minutes.