Evan Mobley had had enough of the back and forth. The USC freshman had sat out most of the first half in foul trouble, watched as Utah hung around in the second, then sneaked into overtime, and then double overtime.

But then, the superstar freshman took over, dominating on defense, imposing his will in the paint.

Even as the fatigue set in for everyone else, as the depth chart was decimated by foul trouble, Mobley flipped a switch in the second overtime, sending USC to a 91-85 win over Utah in a Pac-12 tournament quarterfinal at Las Vegas that required multiple escapes.

“It took everything we had to pull out this win,” USC coach Andy Enfield said.

It took an especially Herculean effort from Mobley, who struggled with foul trouble in the first half only to break out for a season-high 26 points to go with nine rebounds and five blocks.

It was the kind of aggressive performance that coaches had been clamoring for, as Mobley slammed headlong into a freshman wall over the last two weeks, struggling to match his stellar play from earlier in the season.

But as USC (22-6) slogged toward a second overtime, the 7-footer put the weight of the Trojans’ postseason hopes on his shoulders.

“He came in and did what he’s always done,” Enfield said. “He’s aggressive. You might not think he’s aggressive sometimes, but he was very aggressive tonight.”

For most of Thursday’s first half, he was also on the bench, after drawing a questionable second foul on an early charge call.

Enfield had a decision to make — risk further foul trouble from his superstar freshman or rely on USC’s supporting cast to carry the load. He chose the latter, and his confidence in keeping Mobley on the bench wound up paying off.

Isaiah White scored nine in the first half, after missing the Trojans’ regular season finale with back spasms. Enfield said he wasn’t at 100%, but White still scored 14 before fouling out.

Ethan Anderson also helped spark an early 9-0 run with his aggressive play on both ends, ending with 10. And Isaiah Mobley added seven in the first half, stepping in for his brother in the frontcourt.

While the Pac-12’s defensive player of the year sat on the bench, USC’s defense still managed to clamp down, holding Utah without a field goal for six minutes midway through the half.

When Evan Mobley returned in the second half, he quickly reminded why this week he became the first Pac-12 player in history to sweep the conference’s end-of-season honors.

The freshman scored 13 in the second half, and swatted away everything in his path defensively, adding four blocks. But even his aggressive presence couldn’t scare away the Utes, who just two weeks earlier had bested the Trojans on their home court.

Mobley finally took over, scoring eight points in the second overtime period and dominating the paint defensively. The wall he’d hit over the previous two weeks of the regular season was in the rearview.

So, mercifully, was USC’s first difficult test of March.

“It was a long game, a hard game,” Mobley said. “That’s what March Madness, the postseason is. There’s going to be big shots, overtimes, hard games. You just have to stay tough and stay focused.”

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