JuJu Watkins winced, shaking her left hand, the collective basketball world holding its breath. The first 10 minutes of USC’s tournament debut had been disconcerting enough already. Errant passes sailed away. Makeable jumpers clanked away. And No. 16-seed North Carolina Greensboro, having promised to “shock the world,” was at the very least making life difficult on the top-seeded Trojans.

Then, their star sophomore went up for a rebound early in the second quarter and emerged from under the hoop wincing with pain, an image that would inevitably conjure thoughts of the worst possible scenario.

Watkins would eventually shake away the pain. A smothering USC press would eventually put a stop to Greensboro’s plucky start. And the Trojans would eventually roll through their first-round opponent with a convincing 71-25 win, moving on to the NCAA tournament’s second round where they’ll face whoever wins on Saturday afternoon between California and Mississippi State.

That’s not to say it always looked pretty. After the Trojans shook off a slow start, their offense still wasn’t operating anywhere near its peak. Watkins scored 22, but outside of their star, the Trojans shot 19 of 55 from the field.

USC forward Kiki Iriafen attempts a reverse layup against UNC Greensboro forward Khalis Cain during the first half of an NCAA tournament first-round game Saturday.

(Allen J. Schaben / Los Angeles Times)

Even as USC’s bigs towered over most of Greensboro’s lineup, the 16th-seeded Spartans still managed to make life difficult for Kiki Iriafen, doubling her on entry passes and matching her physicality around the basket. The third team All-American wouldn’t score her first point until a few minutes remained in the first half. She finished with 13 points to go with 13 rebounds.

It was USC’s defense that ultimately made the difference. With the Trojans leading by just a bucket, early in the second quarter, coach Lindsay Gottlieb enacted a full-court press, and USC flew into action, disrupting each and every possession from there.

Greensboro didn’t score a single bucket from the field in the second quarter, as it struggled mightily just to get the ball past halfcourt. In the third quarter, it made a single three-pointer … and nothing else from the field.

By that point, the Trojans were already rolling onto the second round. Their defense would allow only 17 points total after a frustrating first quarter. Greensboro would shoot a meager 13%, the worst rate by any USC opponent this season.

Watkins would briefly leave the court in the third quarter, limping to the locker room after rolling an ankle. But she’d return to finish the game, allowing the USC faithful to exhale once again.

USC guards JuJu Watkins and Kennedy Smith celebrate during their rout of UNC Greensboro in an NCAA tournament first-round game Saturday at Galen Center.

(Allen J. Schaben / Los Angeles Times)

Still, the frustrating start was enough to give some pause, as USC looked nothing like a No. 1 seed with Final Four aspirations out of the gate Saturday. They were sloppy with the ball, committing three turnovers in the first three minutes. They struggled to exploit their significant size advantage on the inside — or to knock down much of anything from the perimeter. Two minutes into the second quarter, their lead over the Spartans stood at just two points.

But that’s where the stalemate stopped. Soon enough, USC was moving on, one game closer to where its season has always been leading.