I see 33 rushes, 26 pass attempts per game. That would put the Bills near the top in rushing attempts overall, but not above historical trends.
Barring injuries: (Expect 1 injured RB and 1 injured WR during the year! The names will therefore change.)
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McCoy 20 rush, 4 pass targets ... project to 320 Rush, 64 targets (50 receptions)
RB #2 5.5 rush, 2 pass targets ... project to 88 Rush, 32 targets (20 receptions)
RB #3 1 rush ... project to 16 Rush
Felton 2 rush, 1 pass targets ... project to 32 Rush, 16 targets (11 receptions)
QB 2.5 rush ... project to 40 Rush
Watkins 7 pass targets ... project to 112 targets (71 receptions)
Clay 4 pass targets ... project to 64 targets (40 receptions)
Woods 4 pass targets ... project to 64 targets (40 receptions)
Harvin 1 rush, 3 pass targets ... project to 16 rush, 48 targets (28 receptions)
Others 1 pass target .. project to 16 targets (10 receptions)
Total Rushes: 512 (Would rank #3 in 2014)
Total passing: 416 Att, 270 Comp ... 64.9% Comp Pct (We can hope, right?)
So the above has no basis other than guessing, but I figured I might as well try.