The Trojans beat the Bears 30-20 on Saturday to raise their overall record to 4-0.

It took three quarters and four interceptions for the Trojans to find their mojo in Berkeley.

The spark came from the defense in the fourth quarter, backed up with the Bears’ heels on their own goal line. Senior defensive tackle Josh Fatu hit Cal quarterback Ross Bowers from behind, and the ball popped into the air. Senior outside linebacker Uchenna Nwosu — who spent all day terrorizing the young quarterback — snatched the ball in mid-air, crashing to the ground at the two-yard line.

It was the easiest job that the offense had all day: scrap for two yards in four snaps. They clinched it on the second down with a hand-off to freshman running back Stephen Carr, who powered through two defenders to dive into the end zone and stretch the USC lead over Cal to 23-13.

The 10-point lead was the first chance that the Trojans had to breathe in almost four full quarters of play. A well-matched pair of defenses had brought the game to a grinding halt by the third quarter, but the offense burst to life in the final quarter to clinch the first road victory of the season.

The final score read as expected for a matchup between the No. 5 Trojans and the unranked Bears: 30-20. But USC had to struggle through it, grinding for three quarters of stagnant offense before exploding in the fourth quarter to take the victory.

“We hope that when you get into these games, you can look up and can be a good second-half team,” head coach Clay Helton said. “Credit to our kids. They came in at halftime, took a deep breath, made some changes and really elevated the whole level of play in the second half.”

The defense remained the catalyst for the Trojans as the offense sputtered, but weaknesses at every position were on full display in the first half. Injuries plagued the team on both sides of the ball, with junior linebacker Porter Gustin missing from the defense and playmakers junior running back Ronald Jones II and redshirt senior wide receiver Steven Mitchell Jr. sidelined for the offense.

Highlights came few and far between for the team in the first half of play, as the offense struggled to find any sort of rhythm against a hard-hitting Cal defensive line. In another slow start, redshirt sophomore quarterback Sam Darnold tossed a goal-line interception and took a sack while completing 16-of-24 passes in the first half. He went on to finish the game with 38 completions and 223 yards, but his longest completion was only 19 yards.

“It was such a relentless pursuit to me by the [defensive] line and the linebackers who rushed,” Darnold said. “I felt a little bit of pressure but I think it’s mostly our fault on not connecting on some of those deep balls and some of those opportunities. We need to take advantage of those when they come our way.”

The absence of Jones left an obvious gap as well, as the weight of the USC ground attack fell on Carr’s shoulders. The team picked up only 69 rushing yards on the half, and the result was an off-balance half of play for the offense.

The offense shined for a single drive in the second quarter, the only offensive series to result in a USC touchdown. Junior tight end Tyler Petite stepped into the hole left by Mitchell, snagging two 12-yard passes, while Carr moved the chains twice with runs up the gut. A final 16-yard pass to Petite gave him a curling route to the right corner of the end zone, where he dove to knock down a pylon and tied the game up 10-10.

Yet again, the lack of offense forced the USC defense to stand strong. The defensive line dampened the Cal rushing attack, holding the Bears to 82 yards on the ground, while the secondary forced Bowers to throw for under 50 percent with 13 incompletions. The Bears also benefited from a single full-field march to the end zone, but at the half the defense kept the game level.

“We get more comfortable as the game goes on,” junior linebacker Cam Smith said. “We have a little saying to stay up here, keep the intensity up here and just finish the game off right.”

Both teams entered the second half with something to prove, but a nondescript third quarter left the score tied 13-13. The Trojans found themselves staring down a familiar situation: starting the fourth quarter with no wiggle room between themselves and a loss to an unranked team.

Darnold continued to struggle, rolling out of his pocket time and time again to launch arcing tosses to junior wide receiver Deontay Burnett that couldn’t find their target. He ended the game with only one interception, but struggled to hit receivers and was nearly picked off two other times. Four games into the season, interceptions have become one of the biggest holes in Darnold’s game.

“It’s 100 percent my fault,” Darnold said. “I’m not getting the ball out far enough on deep routes. Whether it’s balls being tipped, not seeing the d-linemen … I’m going to continue to just play, that’s all I can do but, obviously, be more consistent for my team and continue to take what the defense gives me.”

Freshman walk-on kicker Chase McGrath proved his worth again by hammering home a 46-yard field goal, giving the Trojans a 16-13 lead. Despite the thin lead, the Trojans looked peaked.

But Nwosu’s interception breathed new life into both sides of the ball, and the team took its 23-13 lead in stride. Redshirt sophomore Ykili Ross snatched another interception, running it back for 43 yards, and Burnett punched in another touchdown to give the team a 17-point lead.

The Bears kept fighting, but another interception — this time from sophomore cornerback Jack Jones — sent the Cal fans flooding for the exits. The Trojans’ secondary would go on to notch four interceptions on the day as the defense fully denied the Bears a comeback.