USC’s new-look defense aced its first test, but even a five-takeaway spring game victory isn’t enough to satisfy defensive end Jamil Muhammad.

“It’s almost like today wasn’t good enough,” the redshirt senior said Saturday as the Trojans wrapped up their 15-practice spring season, “because we’re hungry. We’re hungry for more.”

Spring practices don’t guarantee much in the way of fall results. Every team ends the sessions cloaked in sun-soaked optimism. Coach Lincoln Riley emphasized his excitement over “the vibe of this team” on Saturday, but good energy won’t be enough in four months when USC confronts the reality of its first Big Ten season. The Trojans still have things to prove at every position.

Here are the main takeaways from USC’s spring practices:

USC’s secondary won the spring game

It might be the team’s steadiest position group.

Miller Moss could sense the difference himself. Throwing lanes were tighter. Windows he was used to seeing were no longer open. There was a swagger, too, about USC’s secondary, one that felt entirely foreign from its last two frustrating seasons.

Last year, USC’s pass defense ranked outside of the top 100 in yards allowed, regularly victimized by big plays down the field. But a new defensive coordinator, a new defensive backs coach and a new scheme, plus some added length on the perimeter, appear to have turned around what was once USC’s most underperforming position group.

At least, that appeared to be the case Saturday, as USC’s cornerbacks picked off four passes, a testament to how much of a difference size and length can make when matched with the right scheme.

“It’s completely different,” said cornerback Prophet Brown, who returned an interception for a touchdown. “I feel like the players are really buying in and stepping up and playing for one another, and now we’re being put in position to make these plays.”

Marcelles Williams looks like a star in the making

Even among such a deep secondary, freshman Marcelles Williams is finding a way to carve out a big role. The former four-star prospect was one of the standout freshmen of spring camp, earning raves from offensive and defensive teammates alike who praised his consistency, maturity and advanced technique honed from years of practicing with his older brother, former USC safety Max Williams.

“He’s a high school senior still,” Moss said this month of the latest Williams brother, “but he can definitely play corner with the best guys on our team right now.”

The former St. John Bosco standout proved his mettle by intercepting a Moss pass during Saturday’s spring game, leaping to snag a ball intended for receiver Ja’Kobi Lane. Williams worked mostly with the No. 2 defense on Saturday as Mississippi State transfer DeCarlos Nicholson and Jacobe Covington started at cornerback. Both were involved in takeaways as Nicholson picked off a pass by backup quarterback Jayden Maiava one play before Williams’ play against Moss, and Covington broke up a pass that led to Brown’s 100-yard interception return.

Offensive line is still far from settled

Although the Trojans are pleased with their top offensive line — Jonah Monheim at center, Emmanuel Pregnon and Alani Noa at left and right guard, respectively, Elijah Paige at left tackle and Mason Murphy at right tackle — they are holding their breath when it comes to depth. Tackle is especially a concern where 6-foot-7 redshirt freshman Tobias Raymond is the next option behind Murphy or Paige. Raymond was 255 pounds when USC coaches started recruiting him, offensive line coach Josh Henson said, and has grown to 314 pounds and is still getting used to the extra pounds.

“His feet have slowed just a little bit,” Henson said last month. “He’s going to catch up. He’s catching back up and he’s figuring it out.”

USC could target an offensive lineman transfer from the portal to bolster the group. The Trojans also expect to have guard Gino Quinones back from a leg injury he suffered last September.

USC needs more depth on the defensive interior

Kobe Pepe had only appeared in a handful of games for USC over the previous four seasons. But on Saturday, with Bear Alexander sitting out because of an injury, Pepe was suddenly the man in the middle of USC’s defensive line.

His rise to that spot was a sign of a looming problem for USC’s defense, one it would be best suited solving in the transfer portal this spring. After 330-pound transfer Isaiah Raikes bailed this spring to re-enter the portal, an already-thin interior is looking threadbare heading into next season.

Alexander gives USC an athletic terror in the middle of the line, but beyond him, there isn’t much in the way of proven talent up front. Redshirt senior Nate Clifton and sophomore Elijah Hughes have both been mentioned as standouts this spring, but neither have the heft needed to man the nose tackle spot. As USC turns to the transfer market, it would be wise to add a proven presence to pair with Alexander in the middle.

Inexperience aside, USC might be just fine at receiver

USC wide receiver Jaden Richardson runs for yardage during the spring game.

(Allen J. Schaben / Los Angeles Times)

USC isn’t going to have much experience at receiver. Nor will it probably have much depth. Of its seven current scholarship wideouts, five will open next season as sophomores or younger, one has never played above Division III (Jaden Richardson) and the other (Kyron Hudson) caught only 17 passes a year ago.

But what it lacks in experience or depth, it may more than make up for in top-line talent.

In Lane, Zachariah Branch, Duce Robinson and Makai Lemon, the Trojans have a more-than-capable sophomore quartet that’s only going to get better over this upcoming season and the next. All four had their moments Saturday, from Lemon’s team-leading six receptions to Lane successfully reeling in a one-handed grab.

Wideouts coach Dennis Simmons made clear early in spring he wanted to add another receiver or two from the transfer portal. That’s to be expected. But if USC’s current young core of wideouts keeps its current upward trajectory, there might not be enough passes to go around.

Woody Marks is in front of running back room

With game experience and leadership quality, Mississippi State transfer Woody Marks has emerged as the starting running back. He is in line to be the third transfer in as many years to take over at running back at USC, following Travis Dye and MarShawn Lloyd. Although Marks is currently ahead of sophomore challengers Quinten Joyner and A’Marion Peterson, Riley expects the underclassmen, including freshman Bryan Jackson, to contribute.

“That’s a nice room right there,” Riley said. “We feel like we can play with all four guys, which I don’t know if we felt like that at this point.”

Joyner had one carry during the spring game and popped it for 16 yards. Peterson and Jackson, both 6-foot running backs weighing 228 and 200 pounds, respectively, add the size and physicality Riley has emphasized at all positions.

USC running back A’Marion Peterson scores a touchdown over linebacker Elijah Newby during the Trojans’ spring game Saturday.

(Allen J. Schaben / Los Angeles Times)

Kicker questions

Denis Lynch is a USC cult hero for his eccentric fashion, but the junior kicker is hanging on to his starting position by a thread.

The former walk-on who was awarded a scholarship last year is 25 of 36 on field-goal attempts for his career, including 10 made kicks on 14 attempts last year. His inconsistency in mid-range kicks — nine of 17 on attempts between 30 and 39 yards — opens the door for competition.

Riley said last month that kickoffs and field goals are “an area we know we have to perform better at.” Besides Lynch, the Trojans have redshirt freshman Tyler Robles, who played in two games last year, including handling kickoffs in the Holiday Bowl. Each kicker made their extra-point attempt during the spring game.