CHAMPAIGN, Ill. (AP) -- Ayo Dosunmu scored 24 points, and Illinois used a swarming defense to upset No. 9 Michigan State 79-74 on Monday night.
Giorgi Bezhanishvili scored 16 for Illinois (8-15, 4-9 Big Ten), and Trent Frazier added 15 as the Illini handed the Spartans (18-5, 9-3) their third straight loss.
Cassius Winston led the Spartans with 21 points. Xavier Tillman added 16.
Illinois led for all but a three-minute stretch late in the game, pushing ahead by as many as 14 points before Michigan State rallied to take a 64-63 lead on Kenny Goins' 3-pointer with 6:21 remaining.
But Illinois, behind its defense, held on and took a 71-68 lead on Dosunmu's 3-pointer with 2:35 left. Dosunmu made another 3 with 1:57 remaining, and the Illini held on from there as the Spartans missed their last four field-goal attempts.
The Spartans were fortunate to stay in the Top 10 after dropping two straight. With Monday's loss, they are likely to fall precipitously.
Michigan State: The Spartans dropped a half-game behind Michigan and Purdue in the Big Ten. The conference schedule has exposed Michigan State's shortcomings without Joshua Langford, who is out for the season with a foot injury. The junior guard had been the main driver of the Spartans' offense.
Illinois: The Illini are on an upswing, having won three of four as their defense has frustrated opponents.
Michigan State hosts Minnesota on Saturday.
Illinois hosts Rutgers on Saturday.