I am not sure that we have someone who is able to fit the second team wing/swing forward role, at least as I envision it. Brissett is 6 ft - 7 in, but had the length to play as a forward. Not quite a PF, more of a big wing. Scheierman and Walsh are both 6 ft - 6 in and both listed at 205 lbs. Maybe Walsh can play as a forward, that is kind of TBD, but it does not seem like Scheierman is going to be a forward. He seems like more of a guard even than Hauser (who is listed at 6 ft - 7 in). Everyone seems to be hoping he can handle the ball like Pritchard and shoot like Hauser, we shall see.
I know the line between a guard and a forward is blurred, and 1 or 2 inches in height is not what matters, it is more about skills and how the player plays on the court. I see a slot on the roster or depth chart for another forward, a wing/swing type of forward. I don't think Tillman is that, he is more of a big. It is not going to be the end of the world if we don't fill this slot, but it would be nice.
I thought Brissett would be better in that role, maybe he can be with another season. I can understand if they decide not to bring him back, even if it means leaving the slot open for a while. Rosters around the league are filling up. There are probably going to be some options for the Celtics to fill this forward role/slot. If it ends up there is no one better than Brissett, maybe they just leave it open.