I'm not really sure this comparison between the Steelers and Falcons holds much water. While Bell is a very good receiving back, he's not quite the same matchup as Freeman and Coleman, specifically Freeman who possesses a lot of speed and short area burst. Bell is big, shifty, and runs pretty good routes, but has a body type that is easier to cover as a LB.
But that's not why I bring this up. I bring this up because Bell, being the great RB/WR he is, got injured very early on in that game. Pats held Williams and Company to 17 pts, not Bell - a Steelers offense that didn't have nearly as many healthy alternative weapons as Atlanta has right now. It's much easier to scheme to shut down a singular player when you can afford to. With Atlanta, the Kyle Van Noy will have his hands full trying to cover Freeman out of the backfield in all that green space Julio provides (Brown is an easier matchup for Butler), while Gabriel runs a crossing route and their TE sits on a zone.