Don't see any reason to be worried about HBA at this point. He didn't come in against Stoke because it was land of the giants and we needed grafters to see the game out.
Best and Ba aren't perfect, they will lose form and get injured, and we'll lose some games soon enough. When that happens the door will be open for petit Hatem to come in and show what he can do.
We all wanted him to set the world alight from day one, but we also never expected the players in the shirts to be doing so well and making themselves undroppable.