Illinois started strong and seemed to be setting itself up for another impressive win after defeating top-ranked Indiana, Gonzaga, Butler and Ohio State earlier this season.
The Fighting Illini, though, were flat in the second half and No. 7 Michigan took advantage.
Trey Burke had 26 points and eight assists to help the Wolverines bounce back to beat Illinois 71-58 in Ann Arbor, Mich.
Illini coach John Groce said Michigan won because its team was tougher and smarter.
"It's unacceptable," Groce said. "It's intolerable."
The Fighting Illini (20-9, 7-8 Big Ten) had won five straight, a run that started Feb. 7 by knocking off the Hoosiers, and were leading the Wolverines (23-4, 10-4 Big Ten) by as much as eight points in the first half.
Michigan outscored Illinois 43-27 in the second half after Groce pleaded with his team to learn from its recent history.
"Coach talked to us at halftime about how we came out strong in the second half and beat Indiana, and how we came out flat and lost to Michigan State," forward Tyler Griffey recalled. "We all listened, and then we came out and played like that in the second half. They really amped up the intensity and we didn't respond at all."
Brandon Paul played a key role in helping the Illini lead 31-28 at halftime – scoring a game-high 10 points in the first half – and was one of the reasons they couldn't keep up the pace. Paul was held scoreless in a shotless second half.
No. 18 Ohio St. 68, No. 4 Michigan St. 60: Aaron Craft slashed through the lane for a career-high 21 points – more than he had scored in the last three games combined – to lead No. 18 Ohio State to a win over fourth-ranked Michigan State in Columbus, Ohio.
The loss crippled the Spartans' hopes of catching up with top-ranked Indiana, which now leads the Big Ten race by two full games with four remaining.
Deshaun Thomas added 12 of his 14 points in the second half for the Buckeyes (20-7, 10-5), who stand fifth in the conference. Evan Ravenel added 10 points and a crucial block in the final minute.
Freshman Gary Harris scored 14 points, and Adreian Payne and Derrick Nix both added 12 for the Spartans (22-6, 11-4), who have dropped two in a row after winning 11 of 12.
Purdue 74, Northwestern 43: Terone Johnson scored 22 points to help Purdue defeat Northwestern in West lafayette, Ind., and snap a three-game losing streak.
D.J. Byrd scored 13 points, and Ronnie Johnson and Rapheal Davis added 10 each for the Boilermakers (13-14, 6-8 Big Ten), who shot 53 percent from the field and outrebounded the Wildcats 48-23. It was the second-largest victory margin of the season for Purdue and the worst loss of the season for Northwestern.
Purdue had lost five of six, and its last three losses had come by a combined 61 points. The Boilermakers were coming off an embarrassing 83-55 loss to No. 1 Indiana, and they had 8 days to think about it.
Tre Demps led Northwestern with nine points. Reggie Hearn, who scored 26 in Northwestern's 75-60 win on Feb. 2, finished with eight. Northwestern (12-15, 5-9) has lost its past three games, all by 20 or more points.