I think the Chiellini injury hurt is game time more than it helped tbh, with Chiellini, Sarri knows he has a good partnership between him and Bon, there is chemistry there and that is the two that would start in a major game. Now he has to get Bon and De Ligt to play together as much as they can to build the partnership for big games, and since they havnt exactly been convincing as a pair its kinda understandable.
Starting Rugani is yuck though, maybe he thinks he can revive him