In my thinking, the uncertainty is with the bigs. You need to cover 96 minutes and I don't think Tatum is going to play all that many of them:
Bigs
Horford 30
Baynes 18
Morris 20
Theis 18
(Tatum 10)
Wings
Brown 32
Tatum 22 (32 Total)
Hayward 28
Rozier 14
PG
Irving 26
Smart 18
Rozier 4 (18 Total)
This accounts for the expectation that Hayward and Irving will miss games for rest and is based on the average over 82 games, not the average in the games they play in. Smart and Rozier get short-changed because of the need to play Morris and Theis more. There will probably be trades or injuries that allow the roster to balance out.