Silas Redd's slow recovery from knee surgery puts the spotlight on USC tailbacks Tre Madden and Justin Davis heading into Thursday's opener at Hawaii.
Redd, the Trojans' leading rusher last season, said on his Twitter feed Monday night that he would not travel to Honolulu with the Trojans.
Junior D.J. Morgan also has not been able to participate in contact drills and is expected to remain home when the Trojans depart after practice Tuesday afternoon.
That leaves the Trojans with only one tailback who has carried the ball in a college game: sophomore Javorius Allen, who rushed for 32 yards in six carries last season.
Sophomore Madden converted from linebacker to tailback during spring 2012 but suffered a knee injury that forced him to redshirt last season, Madden has said he is fully recovered, and he is expected to play a large role Thursday.
Davis, a freshman, also is in the mix to possibly start.
Freshman Ty Isaac was slowed by injuries during much of training camp.