Expected starting quarterback Max Wittek and wide receiver Marqise Lee suffered knee injuries during Southern Cal's first live tackling practice of the spring and will require additional testing.
The extent of the injuries wasn't immediately known, but Lee remained on the sideline to watch practice.
The official report from the team's athletic site: "QB Max Wittek and WR Marqise Lee both suffered knee injuries during practice and sat out the scrimmage. Lane Kiffin announced that both will have further testing before a diagnosis is announced. Lee stood and cheered his teammates throughout the scrimmage, while Wittek rested on the trainer's table with ice on his knee."
Wittek is the favorite to replace Matt Barkley as the Trojans' starting quarterback, giving the team a change at that position for the first time since 2008.
Lee is projected as a high-round pick when he opts to leave for the NFL after catching at least six passes in 10 games as a sophomore last season, including 16 receptions for 345 yards at Arizona and seven other games with nine catches.