PASADENA, Calif. -- While UCLA linebacker Akeem Ayers sprinted up the field with a 77-yard interception return, Houston's Case Keenum disturbingly remained motionless behind him, facemask digging into the Rose Bowl turf.

On the same night the Bruins straightened out their season, the No. 23 Cougars might have headed into a spiral after their star quarterback's latest injury.

Johnathan Franklin rushed for 158 yards and three touchdowns, and UCLA rolled to a 31-13 victory Saturday night over Houston, which lost Keenum for the second straight week when the fifth-leading passer in NCAA history made an ill-advised attempt at a tackle.

"It doesn't boggle your mind. It's football," Houston coach Kevin Sumlin said. "It's unfortunate for us tonight, but UCLA played well and answered the physical challenge. They're a talented team. They were trying to find themselves, and I was hoping it wouldn't happen tonight, but it did."

Kevin Prince passed for 99 yards and rushed for a score as the Bruins (1-2) ricocheted back from a humiliating 35-0 loss to Stanford last week with a stunningly one-sided win. The Cougars (2-1) had the nation's highest-scoring offense last season and again through two games this year after scoring 122 points, but they didn't score a touchdown at the Rose Bowl until James Cleveland's diving 10-yard catch with 11:39 to play.

"We watched so much film throughout the week that we pretty much knew everything Houston was trying to do," said safety Rahim Moore, who returned a second-quarter interception 42 yards from deep in Bruins territory. "With that type of offense being so dynamic, we didn't let it confuse us. You know what's funny? Nobody gave us a chance. They said the defense couldn't make plays. They were giving us all kinds of letter grades that were bad, and we took it personal."

The powerful Cougars' chances for a Conference USA title could be slim without Keenum, who had been the model of durability in his first three seasons.

After Ayers picked off Keenum's throw near the goal line and then dodged the quarterback's tackle in the second quarter, Keenum remained down for two minutes before walking gingerly to the sideline. He eventually left on a golf cart, apparently favoring his right knee.

Sumlin only confirmed Keenum has a leg injury, saying he'll be re-evaluated back home. Houston then lost Cotton Turner, Keenum's backup, to a shoulder injury early in the second half.

"I'm sure [Keenum's injury] affected us some mentally, but when both of them go out, then you have a real effect on what we can do," Sumlin said.

Keenum passed for more than 5,000 yards and led the NCAA in total offense in each of the past two seasons, but the senior incurred a concussion last week while trying to make a tackle after an interception by UTEP's Travaun Nixon. The Cougars didn't confirm he would play against UCLA until he took the field with the offense.

Keenum was 10 of 18 for 83 yards, but also threw two interceptions.