USC running back Tre Madden, who started the first six games last season, could be sidelined for the Trojans' opener against Fresno State because of a toe injury.
Madden's availability will "probably be a game-time decision," Coach
Madden was absent from practice again Friday. He has not practiced since Monday night when the Trojans scrimmaged at the Coliseum.
Madden visited a specialist Thursday and was scheduled to see another Friday, Sarkisian said.
"When you start messing with a running back and his feet and his toes and the ability to push off, they don't just overnight all of a sudden get better," Sarkisian said.
Sophomore Justin Davis is working as the No. 2 tailback behind Javorius Allen. Fullbacks Soma Vainuku and Jahleel Pinner also have played tailback.
Madden was sidelined for the 2012 season because of a major knee injury.
Last season, he rushed for 100 yards in four of the first five games. He was sidelined for much of the second half of the schedule because of a hamstring injury but still finished with a team-high 138 carries and rushed for 722 yards and three touchdowns.
Senior linebacker Lamar Dawson, who has been slow to recover from knee surgery, could be sidelined for at least several games, Sarkisian said.
Dawson started 20 games, including seven last season, before suffering torn knee ligaments during practice.
"He was a little discouraged he's not as far along as maybe he would have hoped for and we would hope for," Sarkisian said. "We just have to get him re-motivated again because he's not that far away."
Catching on quick
Sophomore receiver Darreus Rogers is taking on a veteran's role and helping freshmen such as JuJu Smith, Adoree' Jackson and Ajene Harris.
"I make sure they know what they're doing," Rogers said.
The younger players, especially Harris, also help Rogers.
"Ajene knows everything," Rogers said. "I'm like, 'Can you remind me what I've got?'" on a certain play. "He told me right on the spot."
Quarterback Cody Kessler was held out of drills so that he could rest his arm.
Kessler said he was warming up when Sarkisian told him to take only mental reps.
"I'm a guy that likes to practice," Kessler said, "but what he said makes sense: 'You've already put in the work and I want you to rest.'"
Kessler said he had "been throwing a ton" since training camp began nearly three weeks ago.
"Every quarterback in camp will tell you their arm is tired," he said.
The Trojans were scheduled to do a walk-through on campus Friday afternoon and then go to a downtown hotel as part of the run-up to Saturday's mock game at the Coliseum, which is closed to the media and the public.
Sarkisian said the Trojans would "manufacture injuries" during the mock game to prepare backups for scenarios that might arise during the season.
That includes backup quarterback Max Browne going in for Kessler "in the third quarter, when he's not maybe as warm as he'd like," Sarkisian said.
The annual "Salute to Troy" event will be held Saturday at Cromwell Field on campus….The Trojans will be off Sunday and Monday and then begin game preparations for Fresno State on Tuesday.