The Buccaneers have listed Gronkowski as doubtful for the game against the Patriots, due to a rib injury he suffered five days ago against the Rams. Gronkowski officially did not practice all week, even though he was spotted on the practice field today.
Technically, doubtful means that the player falls somewhere between the broad gulf of just under 50-50 to zero percent likely to play. It doesn’t get used as often as it could, if the goal is to create doubt in the mind of an opponent.
The next question becomes whether he travels to New England. Often, a player on a visiting team stays behind, with his status downgraded to out the day before the game.