Gronkowski had limited participation in the team's practices this week. "Doubtful" is defined by the NFL as "at least 75 percent chance will not play."
Offensive lineman Will Svitek (knee) is out Sunday.
RB Brandon Bolden (knee), WR Aaron Dobson (hamstring), and defensive backs Nate Ebner (ankle) and Duron Harmon (hamstring) were all listed as questionable, and receiver Danny Amendola (groin) was listed as probable.
For the Bills, CB Stephon Gilmore (wrist), K Dustin Hopkins (right groin), and C Doug Legursky (knee) are all out. Safety Jairus Byrd (foot) is doubtful and quarterback E.J. Manuel (knee) is probable.