Unless Gibbs comes bolting out the door like Adrian Peterson, I don't expect to see any of our RBs beating Mason. Gibbs is a special talent, but Mason is pretty talented himself...and he's the veteran that's been in the system for a year.
I know one thing, with the addition of Cochran/Johnson and our other guys returning from health, our RBs will have a good line to run behind. Wouldn't surprise me to see Mason hit 1,000 yards this year. Remember, he was one of the best RBs for yards after contact in the country last season...behind a makeshift line.