At RB i'd go with R. Bush. He has a shitty matchup, but he still has big play ability and your other option Williams haven't really had a single really good game this year. So i'd say this have about the same floor and Bush has a much higher ceiling.
At flex i'd go with Floyd and Tate
8-man PPR league
QBs: Brady RBs: Foster, Charles, D. Martin, Murray WRs: J. Nelson, Fitzgerald, Bowe, Nicks, T.Y. Hilton, M. Williams TEs: Graham, Hernandez K: S. Graham DEF: Texans
Bush at RB, even with split carries he seems to do ok most weeks (plus ppr he gets a few balls thrown his way). At flex I like Tate and Floyd. Honestly I'll take anyone of your options over D Williams, I just don't see it happening for him this week. Tate stock is on the rise as his relationship with Russell Wilson continues to grow, and Floyd has put up 10+ points the last 5 weeks and I think that continues today against the steelers (minus Ike Taylor, that's a plus). Bess had one catch last week, and he is going against an even better defense this week. I expect Hartline to be the star once again in that game.
RB: Williams (he has the better match up and scored a TD against ATL in week 4, Bush is going up against the 4th ranked run defense so that's no bueno). WR: Tate (looks like Wilson likes to go to Tate and he's finally breaking through he should have a good game today) FLEX: Floyd (I'm not crazy about this matchup up against PIT but he's the best option for you based on what you have)
help me out:http://www.fantasyfootballcafe.com/forums/viewtopic.php?t=531772