It will be interesting to see. In some cases it is about the group dynamic. One leader-one "next leader"- one malcontent--you can get the rest from "Snow White and the Seven Dwarves."
Depending on how it shakes out, there is one guy who "will die for the ball". He fights the hardest and the rest take their cue from him.
"Us against the world" is a strong play for a team that is not listed as a consensus favorite. The underdog doesn't have to carry the weight of being the team that is the favorite.
The Titans were good examples of this last year. How about the 1967 Red Sox. They took the heavily favored Cardinals and their roster that included seven hall of famers, to seven games.
Doesn't happen like this in the NBA...that often.
The Celtics don't have "any press to read" this year, so the pressure is off. If one bench guy steps up this year? They will be right there at the end as they have a defensive tradition and that is what wins playoff games.
They are one of the youngest teams in the league and they essentially, don't have "real" veteran leadership...their top players are young.
It helps if there is a common enemy and there is too much work to do before facing the Lakers.