USC running back D.J. Morgan underwent minor knee surgery Wednesday morning, Trojans coach Lane Kiffin confirmed.
Morgan, who has had knee issues dating back to high school, tweeted that he would be out three to four weeks. Under his new practice of not discussing player injuries, Kiffin did not offer a timetable for Morgan's potential return.
Kiffin also declined to say which knee was problematic for Morgan. He tore the ACL and partially tore the meniscus in his right knee during his senior year of high school and redshirted the 2010 season while recovering.
Six weeks ago, Morgan was slated to be USC's No. 2 running back behind Curtis McNeal. But when the Trojans signed Penn State transfer Silas Redd last month, he was pushed back into the third-string role.
Morgan carried seven times for 25 yards in the Trojans' season opener against Hawaii, all of those coming in the fourth quarter with the outcome of the game already decided.
Kiffin said his latest injury underscored the importance of signing Redd away from Penn State.
"It just goes back to how important getting Silas was," Kiffin said. "We’re sure happy to have him."