Anthony Lucas, the Trojans’ new five-star lineman who transferred from Texas A&M, towered over the line of scrimmage, as intimidating as promised. Mason Cobb, who was an All-Big 12 Conference linebacker at Oklahoma State, crouched in the middle, running to every hole with reckless abandon. In front of him was Kyon Barrs, who was an All-Pac-12 Conference defensive tackle at Arizona, holding down the interior with the sort of size USC sorely lacked.

So much of the Trojans’ defense looked different from the group that unraveled at the end of last season, and for the last four weeks ahead of the spring game, optimism had been the overriding narrative. But as quarterback Caleb Williams dropped back on the opening snap Saturday, lacing a 45-yard pass confidently across the field, it was fair to wonder how much a few players plucked from the transfer portal could be expected to turn around a defense on their own.

That question couldn’t be solved with one spring game. But the opening drive didn’t offer much solace. It took just three plays for Williams to lead the Trojans down the field and find wide receiver Mario Williams in the corner of the end zone for a touchdown, punctuating an early gut punch for USC’s defense.

“We knew what we had to fix,” safety Calen Bullock said. “We got to the sideline and was like, ‘Let’s calm down and just play football.’ ”

USC running back Austin Jones (6), right, celebrates with wide receiver Mario Williams after Williams made a first-quarter touchdown catch.

(Allen J. Schaben / Los Angeles Times)

USC’s defense did indeed calm down. It got after the quarterback at times. It clamped down somewhat in the secondary. It even came away with a spring victory over the Trojans’ offense, 42-34, for what that’s worth.

But it never faced Williams again after that first drive, as the reigning Heisman Trophy winner sat after those initial three plays. Three of the defense’s four forced turnovers came against freshman quarterback Malachi Nelson, who struggled to find his footing in his Coliseum debut. Not to mention the defense still had issues against the run, as several running backs, including a pair of impressive freshmen, blew through the Trojans’ front.

Still, afterward, USC coach Lincoln Riley remained sunny about the outlook of his defense. He pointed to a bulkier front seven especially as evidence.

“We all knew deep down that we had some holes there last year,” Riley said. “I mean, it is what it is right? You knew. And even when we’re winning games and playing, playing well defensively, like, you know, at some point this has got to be addressed. It was going to be a focal point no matter if we won five games last year, we won 11, or we won 15 games last year. Like, it was going to happen. And so I’m excited about what that looks like.”

Some changes certainly had been made since last season. That much was clear Saturday. But wheth˜er they’re enough, that won’t be known for a while.