But Kelly expects him to practice Tuesday.
Kelly says Rees was still sore Sunday, although feeling better. Rees was 14 of 21 for 166 yards and two touchdowns before being injured when he was sacked by linebacker Lamar Dawson.
Kelly adds Rees would have to practice a couple times this week to be ready to start Saturday for the Irish (5-2) at Air Force (1-6).
Under backup Andrew Hendrix, the Irish offense couldn't do anything against USC, managing just two first downs as he was 0 for 4. Kelly says he's not sure why Hendrix struggled so much, saying he needs to play better.