USC spokesman Tim Tessalone referred requests for comment to coach Lane Kiffin, who was in a meeting after practice and unavailable.
Ambles, who was not at practice Tuesday, did not immediately respond to an e-mail requesting comment Tuesday night.
Ambles, a native of suburban Atlanta, has played sparingly this season, with one catch for 3 yards in four games. Last month, Kiffin said he actually had intended to redshirt Ambles but was unable to because Ambles had played three plays in the season opener against Hawaii.
In August, Ambles spent one early-morning practice doing rollovers alongside fellow freshman Dillon Baxter -- a punishment Kiffin later attributed to "tardiness."
Ambles, the fourth-ranked receiver in the 2010 class by ESPNU, first committed to play for Kiffin when he was the coach at Tennessee last year but switched to USC when Kiffin left to become coach of the Trojans.
Pedro Moura is co-author of the USC blog on ESPNLosAngeles.com. Follow him on Twitter.