UCLA quarterback Josh Rosen is expected to play against Arizona State

A reason for hope reemerged Tuesday for UCLA on its football practice fields.

He wore jersey No. 3 and is one of the primary reasons the Bruins still have a chance to end their season in a bowl game despite losing three of their last four games and being saddled with one of the worst defenses in the country.

Josh Rosen was back.

The star quarterback participated in practice after having been sidelined by a concussion since the third quarter of UCLA’s loss to Washington on Oct. 28. He is expected to play when the Bruins (4-5 overall, 2-4 in Pac-12 Conference play) meet Arizona State (5-4, 4-2) at the Rose Bowl on Saturday.

“It was good to have him back,” Bruins center Scott Quessenberry said of Rosen, who leads the Pac-12 in passing yards per game (339.1) and is third in passing yards (2,713) despite sitting out nearly six full quarters.

Coach Jim Mora said it became apparent that Rosen “had been affected at some point in the game” after the Bruins’ second drive against the Huskies. Rosen was sacked four times in the first half and threw only five passes in the second half before being removed from the game.

“We think in looking back at it and talking to Josh and evaluating it as we do with all these injuries,” Mora said, “we felt like maybe it happened early and got progressively worse to the point where as tough and as committed as Josh is to playing that it became apparent that No. 1, he was putting himself in harm’s way and, No. 2, he was losing his effectiveness.

“So we immediately removed him from play and put him into our concussion protocol where he has daily evaluations with our medical staff.”

Mora said Rosen was progressing “beautifully” through the protocol and, barring a setback, should be able to play against the Sun Devils.

The question, should Rosen return, is who will catch his passes. Tight end Caleb Wilson and receiver Darren Andrews have been lost for the season because of injuries, but Mora said there was a chance Jordan Lasley could return from the suspension that has sidelined him the last three games because of undisclosed disciplinary issues.

Lasley’s average of 108.6 yards receiving per game in the five games he has played is best on the team, exceeding the averages of Wilson (98.0) and Andrews (85.9).

“We’ve been working with him the last several years, but specifically the last three or four weeks, to try to get him on a path toward consistent success on and off the field,” Mora said of Lasley, “and if he can continue to demonstrate some of the things that we need to see from a behavioral and attitudinal standpoint and accountability and responsibility, then we’d like nothing more than to see him an opportunity to see him go out and do what he loves doing, which is play football for UCLA and help his team win.”

If Lasley is unable to play, UCLA’s primary receivers would likely be Theo Howard (37.0 yards per game) and walk-on Christian Pabico (25.7).

Making a run for it

Soso Jamabo did not carry the ball against Utah after getting more carries than any other player the previous two weeks. It was not an arbitrary decision.

Offensive coordinator Jedd Fisch said the tailback rotation is determined during practice leading up to each game.

“We’re going with who’s practicing the hardest each week and who’s practicing the best and who’s most productive,” Fisch said.

Bolu Olorunfunmi gained a team-leading 63 yards in 16 carries for an average of only 3.9 yards per carry against the Utes, but did show some nice improvisational skills on a few runs, including one that went for 17 yards.

“Bolu ran hard and he trusted his eyes and was rewarded pretty well for it,” Quessenberry said.

Numbers game

UCLA’s man count on defense hasn’t always gone to 11 this season.

The Bruins put 12 players on the field coming out of a timeout against Colorado, leading to a penalty, and had only 10 players after a substitution snafu against Utah in the first quarter. UCLA defensive coordinator Tom Bradley said linebacker Kenny Young tried to call a timeout but could not get one.

Utah tailback Zack Moss then ran through the hole that was created by UCLA’s missing defensive lineman for a three-yard touchdown.

“We’ve got a lot of different groups coming in and out of the game,” Bradley said, “so everybody’s got to be on their toes.”

ben.bolch@latimes.com

Follow Ben Bolch on Twitter @latbbolch