The Gophers (20-12) will play No. 6 Purdue in Saturday's semifinals after the defending tourney champs beat Northwestern 69-61 earlier Friday. It was the second big upset in Indy. Illinois also hung on to defeat No. 13 Wisconsin 58-54 in the afternoon session.
Joseph couldn't win it in regulation, missing a desperation heave as the buzzer sounded.
In overtime, he was the catalyst.
The freshman finished with 17 points and six rebounds as Minnesota won its third straight. Blake Hoffarber had 14 points and five rebounds and Colton Iverson scored 12 points before fouling out.
The Spartans (24-8) were led by Raymar Morgan with 23 points, and Kalin Lucas, last year's Big Ten player of the year, added 17.
Michigan State did play without starting guard Chris Allen, who was suspended by coach Tom Izzo for the game. Allen wore a dress shirt and a green-and-white striped tie as he fidgeted for most of the game on the end of the Spartans bench.
The Spartans trailed most of the night, closing regulation on a 7-0 run. Morgan's layup with 1:30 left finally tied it.
But the Gophers failed to score in the final 3:24, and Lucas tried to win it by driving in for a layup with 3.9 seconds left only to lose the ball out of bounds.
