From the Buffalo News:

For new Bills offensive coordinator Brian Daboll, the lure of returning to the NFL where he had spent most of his coaching career and the chance to return home to Western New York were obvious factors in his decision to leave the University of Alabama.

But was there another factor? The Tuscaloosa News reports that Daboll was frustrated with Crimson Tide coach Nick Saban because Saban wanted to stick with Jalen Hurts at quarterback when the offense was slumping in November while Daboll wanted to play freshman Tua Tagovailoa. The disagreement on personnel matters "weren't all that contentious, but they were frustrating," the report said.