Three quarterbacks, one problem

Ben Olson’s left knee is sore. Osaar Rasshan played down to his experience level in the last game against Oregon. Patrick Cowan hasn’t worn pads since Nov. 3.

One of them, possibly all three, will have to take on a USC team on Saturday that ranks second nationally in total defense. UCLA Coach Karl Dorrell said he would name a starter later in the week.

But the overriding question, no matter who starts or finishes, is whether any of the three can generate the offense that may be necessary against the Trojans. UCLA’s offense has scored only seven touchdowns in the last six games, in part because of injuries.

Of the Bruins’ 29 touchdowns, six have come with the offense off the field -- three on interception returns and three on kickoff returns.

If the game evolves into a shootout, the Bruins could be packing blanks. The Trojans have scored 44 touchdowns.

“We want just to have one more point then they do,” Dorrell said when asked if his team had the offensive capability to win a high-scoring game. “. . . We need to take advantage of every scoring opportunity we get. They have an offense that can put points on the board. Any chance we get to put points on the board, we need to make sure we do it.”

That brings the question back to the quarterbacks.

Olson would seem the likely choice to start, but Dorrell said he wanted to see how his knee responded this week. Olson, who missed four-plus games, started the second half in a 16-0 victory over Oregon on Saturday. He completed four of 10 passes for 64 yards and had one pass intercepted against the Ducks.

“In the back of my mind, he has to show he has progressed,” Dorrell said. “He played 39-40 plays [Saturday] and was sore the day after.”

Dorrell pointed out that Cowan returned from a knee injury to lead the Bruins to victory over California, but hobbled through the next two games before suffering a collapsed lung against Arizona.

Cowan has been cleared to resume practice. Rasshan, who did not complete a pass in seven attempts against Oregon, will continue “to be brought along,” Dorrell said.

As for using all three, Dorrell said, “We’re going to explore anything and everything for us to have some productivity this week.”

The Bruins have leaned on kicker Kai Forbath considerably while the offense has struggled. He has 12 field goals in the last six games.

“We have to put some touchdowns on the board,” tailback Chris Markey said. “We’re not going to be able to just kick field goals against USC.”

The Bruins’ only touchdown drive against Oregon covered 31 yards. In its previous game against Arizona State, UCLA’s only offensive touchdown followed a 68-yard punt return by Terrence Austin to the one-yard line.

“Against USC, we have to focus on the little details or they are going to eat us alive,” Markey said.

For a year, UCLA players and fans have reveled in the Bruins’ 13-9 victory over USC, which knocked the Trojans out of the national championship game.

That seems to be dissipating.

Said UCLA free safety Dennis Keyes: “This is two different teams. We have to forget about what happened last year and think about what we got to do Saturday.”

More so because of what is at stake. USC clinches a Rose Bowl berth with a victory. If UCLA wins and Arizona beats Arizona State, the Bruins play in Pasadena on Jan. 1.

“I think everyone counted us out when we went through our midseason slide,” Keyes said. “Playing this game with a chance to go to the Rose Bowl is crazy. We didn’t envision it happening this way, but it is what our goal was this season.”

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chris.foster@latimes.com