LOS ANGELES — Desmond Claude crashed to the floor, his hands automatically searching for his right knee. His lips tightened, a mix of grimace and incredulity. He staggered to his feet with the help of teammates, unable to put any weight on his leg, heading directly for the tunnel.

And USC’s hopes of knocking off Michigan State seemed to limp right out with him.

He was the engine, and USC’s offense began sputtering in this first half Saturday, trying to hold off a deeper and more athletic Spartans team. Not a few minutes later, though, Claude came back out on an exercise bike. He’d calmed. Head coach Eric Musselman gestured for him to get in, and a team doctor told him to give him another minute. But they had no minutes to wait.

“He said, like, if you’re hurt — out,” Claude recalled Musselman telling him, postgame. “But if you can play, then play.”

“And that’s what I did.”

USC’s leader attacked Michigan State for 34 minutes, on a hobbled right leg, finishing with 19 points. And the rest of a gritty roster attacked with him, for 40, not giving one inch or even one lead in a statement 70-64 upset over no. 7 Michigan State on Saturday afternoon.

“This is a huge win,” Musselman said postgame. “I mean, I don’t know how else to say it. Because, they’re a veteran team, they’ve been in the Big Ten a long time, they’re so well-coached. So this is a huge game for us.”

USC had a student section on Saturday. They had little other semblance of a home crowd, serenaded throughout the day with chants of “Go green, go white!” from Michigan State faithful, USC guard Wesley Yates III facing the unique second-half scenario of being razzed at the free-throw line by his own home arena. They didn’t have Michigan State’s depth, or their cohesion.

But they had a group of hungry transfers, from Claude to Yates III to Saint Thomas, who went full sewer-rat mode on Saturday against a physical Michigan State team. After USC crumpled late to UCLA on Monday, Musselman — literally — placed a weight on his players’ shoulders in a series of intense mid-week practices, players carrying around five-and-10-pound plates through drills and walk-throughs.

“I think it was just kinda the message — if you don’t play the standard, then this was gonna happen,” wing Chibuzo Agbo Jr. said. “So, definitely encouraged us to come out and play a little bit harder in this game.”

They blitzed Michigan State to start, trotting out a specialty defense that operated under “paintball-slash-goalie rules,” as Musselman put it postgame. Against a Spartans team teeming with athletes but light on floor-spacing, USC gave Spartans starting center Szymon Zapala and athletic forward Coen Carr a roughly five-foot cushion on the perimeter, giving the Trojans an extra help-defender in the paint. It stifled Michigan State’s offense early, as USC racked up a quick 22-7 lead.

USC’s offense sputtered to close the first half, as Claude returned but didn’t press the issue much before the break. In the second half, though, he carried USC at every turn: a stepback 3-pointer to beat the shot clock early in the frame, a looping layup off glass the next possession, a consistent diet of pick-and-rolls to initiate offense or hunt his own shot down the stretch and put Michigan State away.

“I wasn’t going to sit out this game,” Claude said. “It just was a big game that we needed. And I had to step up.”

It was gritty. It wasn’t pretty. USC shot 42% from the floor, and committed 11 turnovers against nine assists. But they won as Musselman’s teams have long won: wearing down Michigan State on a parade of late-game free throws, wearing down Michigan State with frenzied defense.