I think it will be both Horford AND White. Horford will play the less minutes but will start and may finish againqt teams with size or superstar at the 4, which make a few team. I prefer Holliday as a clear starter AND finisher because with Brogdon and Smart out WE need his playmaking and expérience.
Not a Big deal all of our big6 will play Big minutes, hopefully not too much for our durability, Mazzula has to imagine and create some new bench guys with unproven NBA level PO guys liké Pritchard, Hauser, Brisset or some players bring by Brad.