USC is looking forward to playing with an experienced secondary this season.
Senior Josh Shaw and junior Kevon Seymour were set to start at cornerback and sophomores Su'a Cravens and Leon McQuay III are returning safeties.
But Seymour's status for the Aug. 30 opener against Fresno State appears uncertain.
Seymour, who did not practice Monday night, is recovering from a stomach ailment that hospitalized him for six days last month. He lost weight and said he has remained on a soft-food diet.
There is no timetable for his return.
"I'll be out here soon," he said.
Coach Steve Sarkisian reminded reporters that the opener is more than three weeks away. So he is being cautious with Seymour.
"I don't want this to linger," Sarkisian said.
Redshirt freshman Chris Hawkins worked in Seymour's spot on Monday. Freshman defensive backs also got more opportunities in Seymour's absence.
Seymour acclimated to the Trojans' new defensive scheme during spring practice, Sarkisian said.