Being inexperienced in big tournaments like this one might be a problem for Graham Potter maybe. They couldn't beat Salzburg for example but it was his first Champions League game at the same time. Chelsea still have four more games to play here. Nothing has ended for them yet but on the other hand they are going to play against Milan two times in a row now. This is the most critical time period of the group stage for them. If they don't get at least four points from these games then their chance to move on can be much lower depending on the results of Dinamo Zagreb - Salzburg games.
Chelsea have actually made the transfer they need for solving their scoring issues. But let's see how good Aubameyang will be able to perform. If he doesn't perform like he was at Barcelona then they might still have serious issues.
Chelsea drop to bottom position standing on group E UEFA Champion League have 1 point, although left four match later I think Chelsea need wake up looking first standing position place AC Milan have 4 points. Chelsea face with Milan on next match and most difficult looking on Milan success lead first standing position now. Graham Potter should give first 3 points for Chelsea if want his position get believing feedback from fans because draw with small team like Salzburg become bad debut for him in UEFA Champion League.
Left two points from second position standing Salzburg I think Chelsea want to get result on another games between Dynamo Zagreb vs Salzburg draw, give advantage for Chelsea if other match draw because not have many different points between second position and bottom position standing awhile. But Chelsea should win against with Milan on next match if want keep existing at UEFA Champion League.