The senior who scored the No. 7 Trojans’ go-ahead touchdown against Ohio State two weeks ago was bench-pressing when the bar slipped from his right hand and fell onto his throat.Southern California tailback Stafon Johnson had emergency throat surgery Monday after a weightlifting accident.Johnson is the Trojans’ second-leading rusher with 157 yards, and he leads USC (3-1, 1-1 Pac-10) with five touchdowns. He led USC in rushing last season with 705 yards and nine touchdowns, but has evolved into the Trojans’ short-yardage specialist this season behind starter Joe McKnight.

Johnson is just one of six tailbacks who get regular practice time with the Trojans, who visit No. 24 California on Saturday. The Trojans didn’t immediately know how long Johnson would require to return from surgery.

Johnson was being spotted by an assistant strength and conditioning coach at the time of the accident Monday morning.Johnson scored two touchdowns apiece against San Jose State and Ohio State, including that 2-yard run with 1:05 left to beat the Buckeyes. He added another touchdown last weekend against Washington State.

Johnson has carried the ball just 32 times this season, while also catching one pass.