Big man depth: I was correct to be concerned about this and the Celtics wisely acquired Tillman for that extra layer of depth. It ended up being vital since Porzingis got hurt and Kornet predictably couldn't play at all against certain teams in the playoffs. Where I was kind of wrong was, Horford maintained the same level of play but I think a lot of that had to do with them having a really easier than normal road to the playoffs. They didn't have to face a Giannis or Embiid. They did face Adebayo but there was barely any other big threats on that Heat team.
Jaylen's role as more of an Aaron Gordon type: I was half right, half wrong about this. Jaylen did become more of a defensive stopper this season and they certainly took advantage of his finishing ability. However, while he scored less per game, he still had plenty of opportunities to initiate and playmake on offense in both the reg season and playoffs. He actually improved weak points in his game like ballhandling, going left, and passing. While he didn't necessarily reach elite levels in any of those things, it was still a significant improvement over how he was before. My original thought was that he'd be more specialized as a play finisher and use a lot of his energy on defense. However, his improvements and impressive conditioning allowed him to still maintain a lot of offensive responsibility.
Backup guard depth: I thought Pritchard would be picked on in the playoffs and wanted them to get a third ballhandling guard that was a little stouter on defense with more size. I still don't think I was totally wrong, because they ended up benching Pritchard in the closing game and just playing 7 guys. I think that the lack of serious threats in the early playoffs helped hide Pritch a bit, until he was just so mercilessly targeted by Luka that Joe was forced to make the change.
Uncertain about Mazzulla: I was concerned that Mazzulla lost the team last year, but I didn't know that Smart and Grant were kind of two of the ones who never seemed totally bought in to Joe's coaching. This year's team was clearly totally bought in and Mazzulla was allowed to shine.