Wrong.....the only reasons Foster would not get significant carries would be injury or a recurring case of fumbleitis. Of the trio of Foster Coker and Hardesty, Foster has shown the most ability, he's not a speed merchant but he is elusive, he almost always makes the 1st guy miss and usually the second, he never gets tackled behind the line of srimmage, he's a good receiver out of the backfield and has been the best blocker of the bunch.
Coker has great speed and can take it the distance when he gets a lane and that's great but he hasn't shown any abilty as of yet to make defenders miss him, he got tackled behind the line of scrimmage time after time against UGA, Bama and Arky, and he can't pass protect worth a damn. If he keeps his nose clean his gamebreaking speed warrants having him on the field alot because eventually he's gonna break one, but to date he's not proven himself to be an every down type of back.
Hardesty, other than the TD run against Cal has shown pretty much nothing, but that may be partly because he was not 100% healthy yet after his knee surgery, this year should tell us more about him but I haven' t see anything about him that makes me think he's the go to guy.
All that being said, any success in the runnig game will depend on the OL, no blocking = no run game.