If USC is to make a deep run in the Pac-12 Tournament and March Madness later this month, it will need to do so on the strength of its bread and butter: defense. The Trojans entered play Wednesday holding opponents to a 39.267% field goal percentage on the season, good for No. 13 in the nation.

But USC took that effort to a whole new level in its penultimate regular season game, a 79-42 victory over Stanford at Galen Center. The Trojans held the Cardinal to an abysmal 6-of-27 shooting — 22.2% — in the first half en route to a 19-point lead at the break.

The 17 points the Trojans allowed in the opening 20 minutes were the fewest they’ve surrendered in a half all season.

“I thought it was very important for us to get off to a good start defensively tonight,” head coach Andy Enfield said after the game. “You could see it meant something to [our players]. They knew they weren’t at their best this past week … We were very tired, we just didn’t have the normal energy that we’ve had most of the season … It was very important for us to get off to a good start defensively and keep that momentum throughout the game.”

If the dominant first-half showing didn’t put the game to bed early, USC’s 14-2 run to start the second half tucked it in and kissed it goodnight.

With star senior forward Oscar da Silva and senior guard Daejon Davis out, Stanford’s three leading active scorers entering the game were junior forward Jaiden Delaire, freshman forward Ziaire Williams and sophomore forward Spencer Jones.

Delaire scored six points on 3-of-14 shooting. Williams posted two points on 1-of-8 from the field. Jones tied for the team-high with nine points on a 3-of-10 performance.

It was that kind of night for the Cardinal, which finished the evening with a 25.4% clip.

The Trojans did more than enough on offense to complement their lockdown defense. Guards redshirt senior Tahj Eaddy and junior Drew Peterson combined for 31 points on an efficient 67% from the field, including 60% from deep, to pace USC on the night.

“[Peterson’s] played really well lately,” Enfield said. “He went into a little slump, he’s out of that slump now, which is great for us because he’s playing at a high level. I think he showed his versatility tonight in a variety of things he can do on the floor.”

What Stanford lacked in offensive production compared to the Trojans, the Cardinal did not compensate for on the glass. USC held a significant rebounding advantage, grabbing 45 boards to its opponent’s 27. Peterson led the team with nine while the Mobley brothers — freshman forward Evan and sophomore forward Isaiah — each collected eight.

It wasn’t a particularly explosive scoring outing for the brothers, as Evan’s 10 points and Isaiah’s seven marked the third straight game in which both brothers played that they’ve been held under 20 combined points.

Other noteworthy performances included freshman guard Reese Waters and sophomore forward Max Agbonkpolo. Waters had a career-high 10 minutes, which Enfield attributed to a strong week in practice, particularly on the defensive end.

Agbonkpolo contributed a season-high eight points on 50% shooting overall and from three.

“My role off the bench is to come in, play defense, guard the best player and then hit the open three when I get the chance,” Agbonkpolo said. “Early in the season, I wasn’t shooting so good. But I feel like now, I’ve got more feel of the game and now I’m hitting my shots … I feel good now.”

The Trojans played a relatively clean game as well — at least, once they settled in. After seven turnovers in the first seven minutes of play, USC coughed the ball up just eight more times in the final 33.

“I think our players were very focused the last two days, and tonight when they showed up, they knew that they had to play well and they wanted to play well,” Enfield said. “They were aggressive, but they also made really good decisions. After the first five minutes, when we just threw the ball all over the place, they made really good decisions and shared the ball and made the extra pass and I thought it was a lot of fun to watch.”

But the story of the game for USC was its defense. The stifling performance came after the Trojans dropped three of their previous four games, allowing 77.3 points per game in the losses — well above their season mark of 65 entering Wednesday.

“March is here,” said redshirt senior forward Chevez Goodwin, whose eight points on a perfect 4-for-4 led USC in the first half. “It’s good to come in with some positive energy … This is the time of the year where, make or break, if you lose you go home. So we had to get back on track and go into March and go into this tournament play with a lot of confidence and a lot of energy.”

USC kept its Pac-12 championship hopes alive with the win, but with Oregon’s victory over UCLA earlier in the evening, the Trojans still don’t control their own destiny. The winner of Saturday’s 1 p.m. contest between USC and UCLA will earn the regular season crown should Oregon fall to Oregon State Sunday; if the Ducks avoid the upset, the conference is theirs for the second straight year.

“We have a game on Saturday. We’re going to worry about our UCLA game and that’s it. We can’t control anything else,” Enfield said. “They’re an exceptional team, they’re very good defensively and we understand how hard it is to win at UCLA. We’re just going to focus on what we can control and that’s to prepare as best we can and play as hard as we can.”