Cowan hurts hamstring; walk-on becomes backup

McLeod Bethel-Thompson received an unwanted promotion late in Monday’s practice, when UCLA backup quarterback Patrick Cowan scrambled upfield, then hobbled out of bounds with a hamstring injury.

That elevated Bethel-Thompson, a redshirt freshman, to second string, at least until Cowan’s injury can be assessed.

“It’s unfortunate, I don’t know what happened to him,” said Bethel-Thompson, a walk-on. “But I saw Pat go down, and it’s my chance.”

Bethel-Thompson proceeded to fumble his first snap, then had a pass batted down on his second play. “Hopefully tomorrow, I’ll do better,” he said.

Cowan, a junior, who started eight games last season, limped off the field, grimacing. He was not allowed to talk to the media.

Quarterback was a position of strength for the Bruins. Cowan led them to three consecutive victories at the end of the regular season, including a 13-9 upset of USC. Ben Olson secured the starting job in spring, but Cowan gave the Bruins a capable backup. That job falls to Bethel-Thompson, who seemed a relative unknown to his coach.

Asked what Bethel-Thompson’s strengths were, Coach Karl Dorrell quickly replied, “We’ll figure that one out.”

But as to what he liked about Bethel-Thompson, Dorrell said, “He’s a very accurate thrower, he has good size, he’s a big kid, all those things. He hasn’t had a chance to do much since he’s been here, he’s going to get a chance now.”

Bethel-Thompson is confident he has a student’s knowledge of the playbook, even if he has had little hands-on experience in practice.

“I know the offense really well on paper, but it’s getting in there and thinking on a split-second decision,” said Bethel-Thompson, who completed five of 11 passes for 46 yards in Saturday’s scrimmage. “Hopefully, the more reps I get, the more comfortable I will be.”

Bethel-Thompson spent part of last season as the backup, after Olson suffered a knee injury. He became the third quarterback this season after Osaar Rasshan moved to wide receiver.

“He’s pretty familiar [with the offense], has he had many reps? No,” Dorrell said. “That’s why we play the game and practice, all those things. Just like at any position, sometimes you’re a play away from being a player. . . . He’s got to be ready to be the second guy in case it’s a prolonged issue.”

Trevor Theriot, a walk-on who could earn a scholarship this season, suffered a hamstring injury late in Saturday’s scrimmage and was held out of practice Monday, leaving the Bruins with Dylan Rush, a converted defensive end, as their only healthy fullback.

“We kept him out just so we can get him back a little later this week,” Dorrell said of Theriot.

Starting fullback Michael Pitre, though, seems more of a concern. He underwent arthroscopic surgery in the off-season, then reinjured the knee Aug. 10. Dorrell said that doctors were in the process of looking over his X-ray and MRI results again.

“We’ll see how the knee responds,” Dorrell said. “We’re still getting more opinions from doctors, just to see where he’s at, but we’re talking day-by-day.”

Defensive tackle Brigham Harwell took a knee to his left thigh during field goal drills. Jess Ward replaced Harwell on the first team. . . . Sophomore defensive end Chinonso Anyanwu missed practice with what Dorrell called a sprained ankle.

chris.foster@latimes.com