Need help with fantasy football?

My second best running back, Kevin Smith from Detroit Lions just went down for the season. I'm in the 2nd round of the playoffs this week, and we start two running backs. I have Ryan Grant solidified as one of my starters. He's not great, but he has been really consistent this year. I have Tim Hightower, Willis Mcgahee, and Kevin Faulk. In free agency, I have the option of picking up Carnell Williams from Tampa Bay, Justin Fargas from Oakland, Darren Mcfadden from Oakland, and Leonard Weaver from Philly. If Westbrook is out again this week I think Weaver might be the best pick. What do you guys think? Remember this is the playoffs, its win or go home.