Who were these players, and what did they do with USC’s defense?

They were physical.

They made open-field tackles.

They kept their team in the game when the offense was stalled.

Finally, in Lincoln Riley’s third year as coach, the Trojans have a defense. Finally, under first-year defensive coordinator D’Anton Lynn, they have a defense that can strike fear into their opponents.

New starting quarterback Miller Moss passed for 378 yards and transfer running back Woody Marks scored a pair of touchdowns, but the most important revelations in the Trojans’ season-opening 27-20 victory over No. 13 Louisiana State were on the other side of the football.

This defense lets the Trojans dream again. This defense could make them relevant on the national stage in ways their recent defenses couldn’t. This defense is why USC could be one of the 12 teams that reaches the College Football Playoff this season.

“This new defensive identity is way different, I would say, than in previous years,” sophomore defensive end Braylan Shelby said.

Countless magicians performed on the nearby Las Vegas Strip on Sunday night, but none were as extraordinary as Lynn, who previously transformed UCLA’s defense into the best in the country against the run.

“Some pretty good Big Ten football today,” Riley said.

LSU drove the ball to USC’s three-yard line on the opening drive of the game but was kept out of the end zone as a fourth-down blitz by linebacker Mason Cobb forced Tigers quarterback Garrett Nussmeier to throw an errant pass.

Cobb also sealed the victory by intercepting a pass by Nussmeier with four seconds remaining in the game.

The Trojans gave up an average of 186.5 yards per game on the ground last season. On Sunday, against an LSU team with a physical offensive line, they yielded just 117 yards, of which 39 were gained on one play.

Shelby said, “We knew what they thought our weaknesses were going to be.”

USC defensive end Sam Greene celebrates with family in the stands after the Trojans’ win Sunday.

(Robert Gauthier / Los Angeles Times)

Basically, that USC would be as soft as it was under Lynn’s predecessor, Alex Grinch.

In interviews leading up to the game, LSU offensive lineman Will Campbell compared the meeting with USC to a “fistfight” and was open about how the Tigers expected to win.

“We’re gon’ run the ball,” Campbell said.

Lynn ensured that wouldn’t happen.

“We needed to turn that around when it came to this season,” Shelby said. “This entire offseason we went in with the mindset of, ‘We need to turn this around, we can’t be known as that.’ This whole offseason was just working on mainly stopping the run. Past seasons, that was a big thing for us, so turning that around was a big thing for us this year and I feel like we are doing that so far.”

Part of the reason the Trojans looked as if they had a new defense was because they, in fact, had a new defense. They started six transfers on defense, including tackles Gavin Meyer and Nate Clifton.

Meyer is listed at 6 foot 3 and 290 pounds, and Clifton 6 foot 4 and 295.

USC defensive end Lorenzo Cowan (37) makes a confetti angel on the field after the Trojans’ win Sunday.

(Robert Gauthier / Los Angeles Times)

“There were points in the game, you could see that for sure, how the size of our defense, how we were much stronger at the point of contact,” Shelby said.

The defense was especially dominant at the most critical stage of the game, after LSU took a 17-13 lead late in the third quarter on a 13-yard reception by Aaron Anderson. The Tigers had a chance to blow open the game. The Trojans wouldn’t let them, forcing them to punt on successive possessions.

The defensive stands allowed USC to reclaim the lead at 20-17 when Moss connected on a 28-yard pass with receiver Ja’Kobi Lane.

“We battled all game long,” Riley said.

With the longstanding problem apparently taken care of, USC’s greatest question mark might now be Riley, who continued to have game-management problems.

He wasted precious seconds at the start of his team’s final drive of the first half, forcing him to decide whether to take a shot at the end zone or settle for a field-goal attempt, which kicker Michael Lantz missed. He squandered two timeouts early in the fourth quarter.

Riley also doesn’t seem entirely comfortable in the spotlight, as he made multiple references to how he doesn’t care what’s written or said about him in the media — usually a telltale sign that a person cares deeply about what’s written or said about him.

However, that’s another problem for another day. For now, the Trojans can celebrate. They have a defense. They have a chance.