I think THB's development could depend quite a lot on the Carabao cup.
At the moment he looks *just* not quite ready. If we get some easy Carabao cup draws in September/October, earn ourselves a dead rubber CL group game and maybe a nice 3rd round FA cup draw, then he could be starting some league games before the end of the season.
Stones is going to get injured, he always does. IMO Pep won't play Fern at CB that often, and I think if the kid has half a dozen assured performances by the time February/March comes around and the title race isn't quite as insanely pressured as it was last season, he could start a few games.
The main thing this season is getting him enough games so that next summer, the coaching staff can judge whether he's up to being 3rd/4th choice CB when Otamendi and probably Fernandinho go.