Hundley, who was being looked at by team doctors on the sidelines, was replaced by Jerry Neuheisel, the son of former Bruins coach Rick Neuheisel.
Hundley was taken to the locker room and is reportedly doubtful to return to the game.
Last season Hundley completed 67.2 percent of his passes for 3,071 yards and 24 touchdowns. He is considered a Heisman Trophy candidate.
UPDATE: Fox Sports reported after the game, a 20-17 UCLA win, that Hundley suffered a slight hyperextension of his left elbow and is expected to be ok by the end of the week.
- Chris Johnson