UCLA lets the air out, escapes with 24-23 win over BYU

UCLA quarterback Josh Rosen found a locker room of support.

The Bruins finished the first half in a funk. Rosen had three passes intercepted, two with UCLA so close to the goal line that the extra-point unit was limbering up.

In the recess of the Rose Bowl, following a first half to forget, there was a moment to remember. UCLA’s 24-23, come-from-behind victory over Brigham Young on Saturday was rooted in it.

Rosen said that Coach Jim Mora pulled him aside at halftime.

“He said, ‘Don’t even think that I’m pulling you, you’re riding this one out,’ ” Rosen said. “Then he started yelling that there were 120 guys in here backing me and everyone was hooting and hollering. It really made me feel good that all these guys had my back.”

Rosen did not win the game. He just managed the offense to victory. The No. 10 Bruins (3-0) had his back.

Running backs Paul Perkins and Nate Starks, following the offensive line’s handiwork, ground No. 19 BYU (2-1) into submission.

Perkins had 219 yards rushing. Starks added 81 yards and provided the finishing kick. He had 60 yards in four carries on the Bruins’ game-winning touchdown drive. He scored on a three-yard run with 2 minutes 13 seconds left.

The defense was on its heels most of the night against Tanner Mangum -- the Cougars’ 22-year-old freshman quarterback. But the Bruins didn’t buckle. They held BYU to two field goals in the fourth quarter and then made a play to clinch the victory.

Linebacker Myles Jack lurked and, then as Mangum scrambled to extend a play, intercepted a pass with 58 seconds left.

With that, the Bruins had lived through the awaited bad game from Rosen and were off to Pac-12 play.

“I’m proud of our young men for never blinking,” Mora said. He went on to talk of resilience and trust that the Bruins showed in getting a “significant win for this program.”

All of which was in the aftermath of a horrific half by a quarterback making his third college start.

Rosen didn’t even have twice as many passes completed (five) as intercepted (three) in the first half. Cougars linebacker Harvey Langi intercepted two passes, the first with UCLA on the BYU nine-yard line. Kai Nacua finished the half by intercepting a Rosen pass in the end zone.

BYU, behind Mangum’s play, took a 10-3 lead into the locker room.

“We can practice situations until we’re blue in the face, but kids don’t grow up until they go through the experience,” offensive coordinator Noel Mazzone said, adding that Rosen learned the lesson that “there are some days where you have to make the plays and there are some days you just manage the game. The second half was a great example of managing the game. Josh made good decisions and didn’t think that every throw he made had to win this football game.”

Rosen said the job was easy.

“It wasn’t my day,” said Rosen, who completed 11 of 23 passes for 106 yards. “We were riding the running backs.”

Perkins finished with a career high in yards. After a 56-yard punt return by Devin Fuller early in the third quarter, Perkins carried five consecutive plays, the last a five-yard touchdown run to tie the score, 10-10.

“Paul Perkins is a beast,” receiver Jordan Payton said. “And the offensive line ... ”

Payton didn’t finish the thought, letting the Bruins’ 295 yards rushing speak for itself. BYU had allowed only 95 yards rushing a game before facing UCLA.

“Coach Mora talked all week about the run game, that the tree doesn’t fall over in one swing,” Rosen said. “You got to keep chopping away. That BYU defense was gassed by that fourth quarter.”

The Bruins’ defense wasn’t depleted at the finish. Mangum, who threw for 244 yards, had carved up UCLA in the first half. He also threw a 14-yard touchdown pass to Mitch Mathews late in the third quarter to help the Cougars take a 17-10 lead.

The Bruins clamped down. They gave up 405 yards, but stopped the Cougars on two key third downs in the fourth quarter, forcing field goals.

Jack then made Mangum pay on a fourth-and-seven play at the UCLA 42.

“I realized they kept running that out pattern and I knew it had to be deep out because it was fourth down,” Jack said. “I jumped the route and it ended up working.”

Mora’s immediate reaction as Jack scrambled about the field was, “I just wanted him to get down. The game was over.”

And the analyzing began.

Rosen had dazzled fans, and the Bruins, by throwing for 351 yards and three touchdowns against Virginia in the opener. Saturday, Mazzone said, “was a great learning experience for him.”

Rosen did throw a 19-yard touchdown pass to Payton in the third quarter to cut the deficit to 20-17. With the Bruins trailing 23-17 midway through the fourth quarter, he opened their final scoring drive with a nine-yard pass to Payton.

After Perkins gained 11 yards in two carries, Starks broke off runs of 31 and 22 yards to put UCLA in scoring position at the BYU seven-yard line before finishing the drive two plays later with a three-yard run.

“[Josh] didn’t play well numbers-wise, but when it mattered, he showed exactly who he is,” Mora said.

Rosen is only going to get better, Payton said.

“The only thing he needs right now is experience,” Payton said. “For him to deal with this situation and for us to win, there’s nothing better than that.”

chris.foster@latimes.com

Twitter: @cfosterlatimes