De'Veon Smith is Michigan's starting running back, no question. He's the only returning back who tallied over 300 yards in 2015, plays the punch-it-up-the-gut game that Jim Harbaugh loves, and has been the most effective rusher this season.
But he's not an all-around back. He's lacking some speed and agility in the catch-and-run game, and the Wolverines have plenty of other backs who can fill those gaps. Why not stick with the by-committee approach?
It's worked so far this season, especially against Penn State on Saturday. All five backs got touchdowns (six total) as Michigan posted its highest rushing yards total of the season at 326 in a 49-10 win.