The emotional leader of the defense was sidelined, his arm in a cast. The team’s top safety was disqualified for targeting, left to watch from the locker room. At the start of a two-week stretch that almost certainly would define USC’s season, its defense was depleted, its scant depth stretched to its limit against Washington State, an offense known for stretching the field to its maximum.

The stage was set for a letdown, with a marquee meeting at Utah looming next week. But after weeks of letting its offense take on a lead role, it was USC’s defense that drew the final curtain, pitching a second-half shutout and willing the Trojans past Washington State in a 30-14 victory on Saturday night at the Coliseum.

Sixth-ranked USC improved to 6-0 for the first time since 2006, when Pete Carroll still roamed the sideline. It had its defense to thank for that.

“You lose two of your best players, two of your leaders …. You gotta step up,” coach Lincoln Riley said. “We had a lot of guys step up.”

A unit that not long ago was considered the Achilles’ heel of USC’s playoff hopes stomped out that sentiment in a hurry Saturday night, even without its injured captain, Shane Lee, at linebacker. The defense held Washington State to 316 yards and completely neutralized Cougars quarterback Cameron Ward, forcing one of the Pac-12’s most dangerous dual threats to run for his life.

Tuli Tuipulotu was regularly the Trojan giving chase, turning Saturday’s victory into a one-man-show of sorts as he tore through Washington State’s line with absolute impunity. The All-Pac-12 defensive linemen finished with three of USC’s five sacks, to go with four tackles for loss.

For the first time this season, USC’s defense didn’t force a turnover. But also for the first time, it didn’t matter much. Known for its propensity to bend but not break, USC’s defense didn’t even do that much bending Saturday night.

It gave up 130 yards and two touchdowns to Washington State freshman Jaylen Jenkins. But in a standout performance, that was perhaps the only nit one could pick.

The concerns, instead, came on offense, where quarterback Caleb Williams was hardly at his best in the face of a disruptive Washington State defense. After opening the game five for six for 86 yards, Williams was 10 for 23 for 102 yards.

“We didn’t throw and catch the ball well tonight,” Riley acknowledged.

With Williams off, USC’s offense sputtered through four three-and-outs. Eventually, Riley turned to running back Travis Dye to put away Washington State. Dye delivered, rushing 28 times for 149 yards and a touchdown.

“You have to win in different ways. You have to find ways to move the ball,” Riley said. “We adapted, and he was a big part of that.”

Dye summarized it more simply: “It was wonderful tonight,” he said of the room he found to run.

Up against one of the Pac-12’s best fronts, it was a stellar showing from the fifth-year senior. Entering Saturday, Washington State had established itself as one of the nation’s most disruptive defenses, ranked in the top seven in the country in both sacks and tackles for loss.

It didn’t appear that way to start.

An offsides penalty from Washington State kept USC’s opening drive alive, and Mario Williams took advantage two plays later, slipping behind the Cougars’ zone, where Caleb Williams spotted him wide open for a 37-yard touchdown, the receiver’s first of two. A field goal on USC’s next possession pushed its early lead to 10, putting the Trojans in prime position once again to push down the gas pedal before halftime.

But as Washington State climbed back, the Trojans stalled. For the first time this season, USC had consecutive three-and-outs. It averaged a meager three yards per play in the second quarter.

In the meantime, the Cougars kicked into gear, sparking a 92-yard scoring march capped by a 12-yard touchdown to Robert Ferrel. When they quickly got the ball right back following a Trojans three-and-out, a targeting call sparked yet another touchdown drive.

The penalty would leave USC without Calen Bullock, its top safety, while completely changing the early tenor of the game. A USC stop that would’ve forced Washington State into third and long instead left Ward, two plays later, to test the Trojans deep. There, he found running back Jaylen Jenkins, who pulled down a circus catch from 45 yards that set up an easy, go-ahead score for Washington State on a one-yard pass to Nakia Watson.

Penalties continued to turn the tide in either direction. An offsides call breathed life into USC’s ensuing drive, which seemed certain to stall in the red zone. Facing third and long, Caleb Williams lofted a pass to the corner of the end zone, which yielded a fortunate pass interference call. Dye scored from four yards out on the next play.

It took another timely penalty for USC to punch in its next touchdown. What would’ve otherwise been an interception thrown by Caleb Williams in the third quarter wound up nullified by defensive holding. An unsportsmanlike conduct call tacked on another 15 yards, and Mario Williams made Washington State pay for its mistakes with his second score, on a 24-yard throw.

USC’s offense produced just two field goals in the fourth quarter. But its defense had dug its claws in, proving that it could carry its own when called upon.

“Defense has led us to some huge victories, and I’m proud of them,” Riley said. “I know there’s more there. We’re going to keep getting better.”

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