USC quarterback Mark Sanchez overcame a dislocated kneecap in training camp and other physical setbacks to enter Saturday's game against California as the Pacific 10 Conference's passing efficiency leader.
Sanchez, however, turned in perhaps his grittiest performance of the season during practice Thursday after suffering an ankle injury, apparently during warmups.
Sanchez missed a few early drills while getting his ankle and foot taped, and then rejoined the workout with his shoe wrapped to the size of a small football. The junior took all of the first-team snaps, but hobbled on rollouts after handoffs, grimaced repeatedly when out of view from teammates and conversed several times with team trainers.
Coach Pete Carroll said he was unaware of any problem with the quarterback, who has recently been counseled by offensive coordinator Steve Sarkisian to keep his emotions in check while moving from one play to the next.
Meantime, tailback Joe McKnight made it through the week without aggravating a toe injury that forced him to sit out two of the last three games. Carroll said the sophomore would play against Cal.
"I've been kind of holding my breath a little bit because I want to get him back out there and get him on the field for us," Carroll said. "Having [Friday] and all the way till Saturday night helps him as well.
"He looked 100% out here practicing all week long and he was determined to show that too."
USC remains unsure about who will start at quarterback for Cal.
Kevin Riley, a sophomore who suffered a concussion last week against Oregon, returned to practice Wednesday. But there is still a chance that Coach Jeff Tedford could turn to senior Nate Longshore.
Riley, 6-2, 224 pounds, is more mobile and is 5-1 as a starter this season. He has passed for 10 touchdowns with three interceptions.
"I've always said that the guys that can run the football make it harder on you," Carroll said. "If Riley's out there running around, making things happen with his legs, then that's the unpredictable factor."
Longshore, a 6-foot-5, 233-pound senior from Canyon Country, is a pocket passer. And a known quantity.
Longshore completed 13 of 29 passes for 199 yards with an interception in a 24-17 loss to the Trojans in 2007. In 2006, Longshore was 17 of 38 for 176 yards with two interceptions and a fumble in a 23-9 defeat at the Coliseum.
Longshore has passed for eight touchdowns with four interceptions and is 1-1 as a starter this season.
Nick Howell will start for the fourth consecutive game at right tackle, Carroll said. Defensive tackle Averell Spicer (ankle) will not play. Tight end Blake Ayles (knee) is expected to be held out.