Of the people we know who are available (well, at least rumored to be), Diggs is the only one I would seriously consider. Another strong receiver would be a bonus.
I would never trade for a Running Back, remember, we let one of the all-time greats walk before the season started. Why? Because the ROI for backs is never high, there are serviceable people out there on Practice Squads and even street free agents. Either can be had relatively cheaply.
As for Trent Williams, it appears the price is too high, but that could change. I do think, however, if the injuries are serious to Ford and Morse, they may make some kind of move here. The wild card in this is Bates. We know Long is a capable starter--he has proven value. But Bates seems to be the steal of off-season. Somehow Beane had him targeted, pulled it off, and by all accounts, that appears to be a brilliant pick-up. If it turns out he has to play regularly, it is even better. Having another starting quality o-lineman would be a bonus.
Which brings me back to WR. I'm still not sure what we have here. Foster is the enigma right now. He showed great potential last year, but injuries have hampered him this season. I love the Duke story, and what we saw from him yesterday is what he will bring--a good possession guy who will not out-run anyone, just out muscle them--which is good. We seem to be missing one more capable person. I'm sure they thought that Zay, maybe Foster, would be that third wheel, but this is a meritocracy business and you have to produce in games, neither has. So, if (and that's a big "If") the Bills do anything big, I think its in the WR position--that is the one place an immediate impact could be a difference maker.