Who to start at QB??? Matt Cassel, David Garrad, or Kerry Collins?

I need help I`m in the playoffs and I had Aaron Rodgers(GB) and he went down with a concussion and is out. Their are good amount QBs to pick up but I narrowed it down to Matt Cassel(KC) David Garrad(JAC) and Kerry Collins(TEN), Curious who I should go with and why. (ALso if their is any other QB you think are worth picking up then please let me know.