EVANSTON, Ill. -- Michigan State built its 15-game winning streak on solid, consistent play and an ability to defend an array of teams and approaches.
The Spartans (No. 7 ESPN/USA Today, No. 6 AP) matched up Saturday against a style they couldn't contain.
Northwestern stars John Shurna and Drew Crawford got their points and their shots, but what really hurt Michigan State was the play of backup center Davide Curletti, who made his first start of the season and second of his career.
Curletti had a season-high 17 points and six rebounds, and his hustle helped the Wildcats pull of an important victory for their NCAA resume -- an 81-74 victory over the Spartans.
"Curletti was the difference in the game, if you ask me," said Michigan State coach Tom Izzo, who fell to 26-4 against the Wildcats in his career.
"I thought he played extremely well and outplayed our centers and that's something we've been pretty solid on lately," Izzo added.
Shurna had 22 points, 13 in the second half, and Crawford had 20 as the Wildcats (12-5, 2-3) rebounded from a tough overtime loss at Michigan three days ago.
Michigan State (15-3, 4-1) lost for the first time since it was beaten by Duke at Madison Square Garden on Nov. 15.
Izzo was worried about his younger players and how they would handle Northwestern's Princeton-style offense -- with its array of picks and cuts -- as the shot clock was running down.
But he didn't expect the Wildcats to get such a lift from Curletti.
"It is fun when you play well like that, helping other guys is a great feeling, especially for us," said Curletti, who also had four assists. "Our offense is built around each other, making back door cuts, making back door passes. ... We were barely ever out of our offense and we were able to really run it to perfection."
Northwestern shot 54 percent in the second half, finishing right at 50 against a team that was allowing just 37 percent all season. Teams had been averaging just 59.6 points against the Spartans through the first 17 games.
"We didn't lose that game on the offensive end, we lost it on the defensive end," Izzo said. "We're not allowed to give up 81 points. It's ridiculous."
Keith Appling led the Spartans with 17 points, and Draymond Green had 14 points and 14 rebounds. Michigan State shot 65 percent in the first half and went cold in the second 20 minutes against Northwestern's zone.
"The main thing was stopping them in transition because they have so many fast guards," said Crawford, who has been battling the flu. "Once we were able to stop them in transition, we're confident in our zone in the half court and we were kind of able to slow them down a bit, which really helped us out."
Northwestern fans stormed the court after the victory, perhaps a pivotal one for the Wildcats as they shoot for the first NCAA tournament berth in school history. They needed the win badly after the loss at Michigan and one in their previous game at home to Illinois.
Crawford hit a jumper and then made a 3-pointer as Northwestern extended its lead to six points 5 minutes into the second half -- with the help of five straight missed shots by the Spartans.
Even after playing good defense, the Spartans had trouble controlling Northwestern.
Shurna put up a wild shot to beat the shot clock but teammate Reggie Hearn sailed through the lane and followed it up. Then Curletti broke for the basket on a back door play and dunked to give the Wildcats a seven-point lead with just over 12 minutes left.
After such a torrid shooting first half, the Spartans missed 12 of their first 15 field goal attempts in the second. Shurna broke free for a layup and minutes later had a dunk as Northwestern increased the lead to 12 with 8:32 left.
State rallied with a 7-0 run started by Travis Trice's 3-pointer and cut the lead to 69-64 with 5:32 left. But Dave Sobolewski hit two free throws and Shurna made another 3-pointer from the top of the key and the lead was back to 10.
Michigan State made nine of its first 10 shots, including 4 of 5 from 3-point range. Green hit three straight early 3-pointers and the Spartans led by as many as nine, having little trouble with Northwestern's defense early.
But the second half was a turnaround. The Spartans shot 34.4 percent (11 for 32) in the final 20 minutes and were only 4 for 11 on 3-pointers.
Izzo, still two wins shy of his 400th career victory, looked back at the first half when the Spartans had several leads and a couple of missed opportunities, and allowed Northwestern to wrestle rebounds away and score. On one of them, Curletti converted a three-point play.
"Probably the biggest thing was hustle plays. We had rebounds they took from us and scored three different times. ... Each time we had a six- or seven-point lead and they took it and laid it up. One time they made a three-point play. That became the difference in the game."