I predict this will not be a very important questions this season for health reasons.
Horford missed 19 games last year, I expect he'll miss a similar number this year. Porzinigis is more than likely to miss time with injuries here and there. Jaylen typically misses at least 15 games with some nagging thing, same for Jrue who is getting up there in age. Tatum usually misses a few. White is an iron man.
If Horford misses 20 games, Porzingis 15, Jaylen 15, Jrue 15, and Tatum 5... that's 70 games where we're missing at least one starter.
Injuries never line up so conveniently but I think there are going to be a lot of games this year where the top 6 aren't all available so we won't have to worry about this too much. Those handful of games where we do, maybe it can be match-up dependent.