Add Kyrie and Hayward to the current group and you have reason to feel very optimistic.
IMO after the 1st quarter, this young Celtic team saw themselves going into the championship series and a few players decided that it wasn't time.
The debate about Rozier taking over Kyrie's PG spot is over. The scary thing about Terry is just which Terry are you getting each night. Because when Rozier isn't hitting his shot he is useless. He makes nobody better. He spends the entire remainder of the game looking for his own shot. He is a two guard in a PG body.
Jaylen Brown has a confidence problem. That's why he has a confidence coach. If you want to see where his confidence is on a certain night, just watch his free throw shooting. When he looks scared, robotic and uncomfortable on the free throw line... it's because he is, and it's not going to be his night.
When injuries to Hayward and Irving happened, the basketball IQ on the team really suffered. Depending on Smart, Rozier, and Morris to make consistently sound basketball decisions is futile.
Tatum is a superstar waiting in the wings, the kid is cold-blooded and very talented. He wants the ball when the game is on the line. We're seeing the tip of the iceberg here.
IMO re-sign Smart, and Baynes if you can, if a major big man becomes available, there are a few players I would include in a trade for him.
If not...we'll still be just fine for years to come.