LOS ANGELES — Nine plays in, USC’s much-ballyhooed QB change had begun in disaster with an airmailed pick-six, and Lincoln Riley rested his hand on his young quarterback’s shoulder pad on the sidelines and spoke in sweet reassurances.

Trust your eyes. Go through your reads. Continue to execute.

All fine. All well and good.

Jayden Maiava, really, needed no reassurances.

Yes, he’d just made a grave mistake on the second drive of his first start as USC’s starting quarterback. Yes, he’d been tossed into fire with Miller Moss’ benching, and immediately had raked his own program over the coals Saturday afternoon. But the kid had been a playmaker, from his earliest days on O’ahu to his earliest days in USC’s program, and there was an inherent degree of risk involved in his cannon arm and freewheeling legs.

The reward came, quickly and often and plenty in the quarters to come, as Maiava wrestled sheer chaos to his will for the better part of a 28-20 USC win over Nebraska that validated Riley’s trust in him as these Trojans’ starting QB down the stretch.

“I know he was excited, nervous, all of that for — his first opportunity to really play here at USC,” Riley said postgame, of Maiava. “I thought he handled it well, especially when you start off like that — that’s, like, the last thing that you want to happen.”

“And his response, and the team’s response, was very key.”

Before he was a quarterback, the 6-foot-4 Maiava was a receiver on fields across O’ahu, playing in a youth league coached by Tua Tagovailoa’s father, Galu. And the same traits in him today, the former youth coach said, have been present since Maiava was running free across the ocean in middle school.

“No matter how bad the play is, and when things are broken ... just, you see Jayden trying to make something happen,” Galu Tagovailoa said. “And that’s just how that kid has been.”

It’s how that kid was on Saturday, wholly unafraid even as he started out 2 of 7 for 12 yards and a interception — to USC-turned Nebraska transfer cornerback Ceyair Wright, no less — returned 46 yards for six points to put USC in an early hole. He returned to the sideline, sophomore Duce Robinson recounted postgame, and tapped his receivers on the shoulder.

“That’s on me,” Maiava told them.

A minute and 30 seconds of game clock later, Maiava rolled on a third-and-7 and threw an 18-yard strike just past the fingertips of a Nebraska defender for a first down to senior Kyle Ford.

“He’s gonna take risks,” linebacker Easton Mascarenas-Arnold said of Maiava. “And some go his way, some don’t, and that’s kind of why he’s gonna be such a great player. “Because he’s willing to take those risks over and over again, regardless of the play before.”

He took them, again and again on Saturday, to glory and to pain. Four plays after the strike to Ford, he ran for his life away from Nebraska pressure and flung a desperation heave to Robinson — trying to throw a ball that was “either his ball or nobody else’s ball,” as Maiava put it — for a miraculous 28-yard completion. He hit Zachariah Branch for a short score to finish off the drive, hit Kyron Hudson on a bobbled-and-caught end-zone grab at the start of the second quarter, bombed a 48-yarder to a wide-open Robinson in the middle of the third.

And then, with USC up 21-17 on Nebraska in the third quarter, he took a risk wholly too far, trying to evade a Nebraska pass-rusher back at his own 26-yard line and getting strip-sacked in a potentially catastrophic play.

When asked postgame if he felt he tried to do too much at times, the even-keel Maiava responded with an emphatic “no doubt,” a problem he affirmed he’d had dating back to his previous freshman season at UNLV.

“That’s just me being me,” Maiava said. “I mean, obviously — it’s rough. But I’m glad that it happened to me, just so I learn from it.”

USC’s defense, though, picked up the slack at every opportunity, in a tour-de-force performance from coordinator D’Anton Lynn and personnel. After a brilliant second-quarter pick, cornerback Jaylin Smith raised his hand to his helmet on the sidelines to mime an apparent shark-fin, a gesture mimed throughout the night by his USC teammates.

“I brought it to the offense, like, ‘We the shark gang,” Smith grinned postgame. “Shark gang.”

To be more specific, as Smith explained: the act of swarming to the ball, on defense. And Smith and company swarmed, for the entire second half. Linebacker Mason Cobb came up with a massive third-down red-zone stop after the field flipped on Maiava’s fumble. Safety Kamari Ramsey, healthy after multiple absences, had another, preserving a one-point fourth-quarter lead after kicker Michael Lantz’s field goal was inexplicably blocked the previous possession.

And on a subsequent drive chewing seven minutes of clock across 13 plays, USC finally found the late-game offensive execution it’d been looking for all season. Facing a fourth-and-one from Nebraska’s 47-yard line, Riley dialed up a fake-jet-sweep-pitch to Woody Marks that the stalwart back took for 34 yards.

“Coach Riley was in his bag,” Maiava said postgame, on the play.

And with three minutes left and the ball at the 2-yard line, Maiava took a keeper and darted past a Nebraska defender, a born playmaker seizing his moment for the score that finally closed a game for USC.

Maiava finished 25 of 35 for 259 yards, accounting for four total touchdowns and two turnovers. Marks eclipsed 1,000 yards on the season with a year-best 146-yard performance on the ground. Cornerback Greedy Vance Jr. picked off a last-gasp Nebraska try in the end zone as time expired — despite a missed pass-interference call — and handed the ball to athletic director Jen Cohen for the cherry on top.