The Patriots are probably smart enough to realize that RB is the most fungible position in football, and they don't need the McFadden PR splash that every other team picking in that area of the draft will covet. They'll likely either take somebody like Dorsey or trade down.
Unless, of course, Belichick wants to just turn the screw in a little more by following up 19-0 by taking the biggest name in the draft -- in spite of the fact that their first round pick was taken away. I can see that happening too.