USC tailback Stafon Johnson got just three carries in the Trojans’ recent scrimmage, but it’s part of his plan to become a better player this spring. “I’m maturing a lot,” Johnson said. “I’m getting an opportunity to catch the ball out of the backfield. There are plays I wanted to work on catching the ball in spring along with pass protection.” Johnson should be a favorite to start next season after backing up the departed Chauncey Washington, but he’s part of six tailbacks trying to play for USC.