Tough fantasy trade decision.... rashard mendenhall for fred jackson and roddy white?

I'm in a very tight leauge. Aside from mendenhall I have adrian peterson, Larry fitzgerald, mike Williams (tb) and dez bryant as my regulars... oh and mike Vick!!! this would be a move made with someone I could be facing in the playoffs and his team is fairly deep already (tom brady, Michael turner, arian foster). I'm just worried about mendenhall sharing too much time and also the steelers heavy p game as of late. Help plz!!!