Danny Kelly has been ranking position groups over at the SB Nation NFL site, and his latest installment addresses the running back position.
Kelly puts the Buccaneers in the 'elite' group, along with the San Francisco 49ers, the Buffalo Bills and the Cincinnati Bengals. Assuming Doug Martin can get healthy and back to his 2012 form (his 2013 play was at times unsteady), this seems pretty fair. Muscle Hamster probably isn't a true elite running back (at least compared to Adrian Peterson and Marshawn Lynch), but the depth at the position pushes the Bucs into the elite category.
It's one thing to have a bell-cow running back capable of consistently handling the load (which they certainly do). It's another entirely to have another pair of running backs who have been productive as lead backs (Bobby Rainey and Mike James), another back who did exactly that in college and was highly productive as a pass-catcher to boot (Charles Sims), and one of the fastest players in the NFL (Jeff Demps).
That's top-end quality. That's depth. That's the kind of production and potential that really, no other team in the NFL can replicate. It looks and feels like they want to do what the Philadelphia Eagles, the San Francisco 49ers and Seattle Seahawks have done over the past years: make the running game the core identity of the offense. You can't do that with just one back, and the Bucs have repeatedly stated that one back won't be able to carry the load. Depth is crucial in the NFL.
Still, a lot of this depth is pretty speculative. Mike James looked very good last year, but he lasted all of 60 carries. Bobby Rainey looked solid if unspectacular, but he really only had a pair of games where he really carried the offense -- the running game's production down the stretch really fell off. And while Charles Sims looks like a pretty good addition, draft picks are never sure things. And ultimately, you'd rather have an elite group of defensive linemen or (ideally) quarterbacks, than an elite group of running backs.
On paper, this looks like a really strong group. The kind of group you can build an offense around. They just have to go out and show up, now.