This is pure speculation, but this feels like Mike Pettine to me... as Nathaniel Hackett and Mike Pettine were both coordinators of the 2013 Bills. Doug Marrone was a first time NFL head coach, and the same Doug Marrone that just fired Hackett as they're both with the Jaguars.
The 2013 Bills went 6-10, BUT that's with rookie EJ Manuel starting 10 games, and Thad Lewis/Jeff Tuel (who?) for the other 6.
They picked up more than 2,300 rushing yards mostly behind Fred Jackson and C.J. Spiller.