I don't expect Shane Vareen to play vs Carolina and if he does I expect him to have a limited role because of his injury. But I think it's important to take a look at what Vareen will bring to the Patriots as he progressively returns.
First things first, despite the patriots recent outbreak vs the Steelers the offense has been bland and relatively ineffective. Vareen won't be able to doctor many of these problems ( he can't catch the ball for Thompkins and Dobson) but he can create a pressure release valve for Brady when he drops back. Rather then having to force the ball to tightly contested receivers Brady will have the ability to dump the ball down to Vareen and just watch him pick up yardage. Vareen has better hands then bolden who has been playing the scat back role and also is more explosive in open space then any of the running backs. Having the option to throw short to the safety valve and pick up chunk yardage after the catch will take some pressure off of Brady and the offensive line.
Speaking of the offensive line the Patriot's line could use some help in pass protection and Vareen is just the guy to help. Vareen is just a standard blocking running back but he can help the offensive line with his speed and ability in open space by utilizing screens. When the patriots line up in passing situations they will be able to snap the ball and let the opposing linemen attempt to get after Brady then sneak the ball to Vareen in open space with blockers. The simple screen game can help neutralize opponent pass rushes and get Brady in rhythm with simple passes.
Lastly in my opinion, Vareen will have his biggest impact with his versatility. Although Ridley, Blount, And somewhat Bolden are all geared towards tough downhill running, Shane Vareen has much more offensive versatility. The Patriots will utilize Vareen with shotgun runs, wheel routes, and splitting out wide as a wide receiver. The great versatility that Vareen possess can cause matchup problems most notably a linebacker attempting to cover Vareen one on one. Look for Brady to exploit any matchup problems caused by Vareen's versatility