Honestly, Chelsea has had a pretty uninspiring off-season.
Didn't like the Sterling signing to be honest. He's a good player when he's on it, but he is fairly inconsistent. I would have even taken Ronaldo for one season over signing him. At least you know that you'll get a player that guarantees goals.
The Koulibaly signing was basically a replacement for Rudiger. Koulibaly may be marginally better than Rudiger, but you also lose someone who was a leader at the club.
So where has the squad actually improved? I don't see it. If I were Tuchel, I would appeal to the owners and let them know that this is a season in transition. The club lost a long-time owner who left somewhat acrimoniously and was beloved by the players. At this stage, the club is one that lacks an identity, and that's why you see players looking to leave, or players somehow reluctant to come.
I'd go all-in and just play the youngsters. Give Gallagher, Broja, Ampadu etc a shot. Club is in desperate need of a creative mid a la Modric, and a 20 goal a season striker. It doesn't have any of that right now. Build on your academy talent for the season and open up the books in the next transfer window.
It didn't even take the thumping against Arsenal to see it, but I felt that Chelsea would be fighting for a fourth place position this season. I see Man City first, Arsenal second, Liverpool third and Chelsea battling for the fourth spot with Tottenham. I know people will disagree with Liverpool, but they've just sold off three attacking players and basically brought it one. They have been fortunate with injuries these past couple seasons (van Dijk aside), but they really lack squad depth. Man Utd has not really improved at all as far as acquiring players.
Other issue Tuchel may be faced with his player discontent. Chelsea has a history of players mutinying against coaches. If he can't shore up the dressing room, then they risk even sliding down mid-table.