Running back Maurice Drew's status for Saturday's game against USC remains questionable after the sophomore left practice early for the second day in a row on Tuesday.
"Maurice did some individual stuff early ... but he's still pretty sore," Coach Karl Dorrell said. "The likelihood is probably 50-50" of Drew's playing against the Trojans.
Drew, a second team All-Pacific 10 Conference selection as a running back and punt returner, has not played since he suffered a high ankle sprain in the first quarter against Washington State on Nov. 6.
Drew did not play in UCLA's victory at Oregon on Nov. 13 and hasn't completed a full contact practice in nearly a month.
"He's going to need to practice and do some things first," Dorrell said about Drew, who is 13th in the nation in all-purpose yards at 159.56 a game.
"We have to see how effective he is on the practice field. I'm sure that we'll have a better idea on Thursday."
Drew leads UCLA in rushing with 886 yards, which includes a 384-yard effort against Washington. In last year's game against USC, Drew caught four passes for 76 yards and returned a kickoff 99 yards for a touchdown in the Trojans' 47-22 victory.
If Drew does not play, senior Manuel White will start with freshman Chris Markey as his backup.
In last year's game against USC, quarterback Drew Olson established a personal best with 266 yards passing. He completed 21 of 39 passes with two touchdowns and one interception.
But the Trojans led, 30-0, before UCLA scored a point. Olson says he expects the Bruins to make a better showing against USC's defense.
"If anything, I'm excited about going against their secondary," Olson said. "I'm looking forward to going against them, but that's not true with their D-line.
"They do not rely on their secondary because of the strength of their front four and front seven. They don't give you a lot of time. You're not going to be able to be back there all day waiting for someone to get open."
Olson said the key would be how well UCLA runs the ball.
"We'll get our opportunities," he said. "Their secondary is probably the weakest part of their defense, not that it's weak. But compared to their other areas, it definitely is not as strong.
"If we're able to run the ball, that will be a big factor. They bite on play action and stuff like that. They are real aggressive."
Dorrell on redshirt freshman Chris Horton, who has returned to practice this week after sitting out the last three games because of a foot injury: "He's ahead of schedule and he's getting reps" with the second-team defense. "We anticipate him to play on Saturday and that's been a good surprise for us."
Quarterback recruit Ben Olson, rated among the top high school prospects in 2001 out of Thousand Oaks High, attended practice on Tuesday and said that he would take an official visit this weekend with the Bruins. Olson, expected to be on the UCLA sideline on Saturday, said that the Bruins along with Arizona State, Oregon and South Carolina with Coach Steve Spurrier were among the schools he was considering. Olson, not related to Drew, spent one redshirt season at Brigham Young. He said that he hoped to narrow his choices within the next couple of weeks.