I'm afraid Chelsea couldn't start the friendly matches well.

First a draw against Wrexham and now a huge defeat by Celtic, 4-1. Maresca is new around here of course but hopefully he manages to find the right system for the team soon.
Though I wasn't expecting Chelsea to lose their preseason friendly game against Celtic, I wasn't also too surprised to see them suffer a defeat in the hands of the Scottish club since it wasn't a competitive game. Chelsea new manager I believe is still trying to establish his own style of football in the team which I think will take some time for him to perfect it. Chelsea under Enzo Maresca is still a work in progress and I believe they'll get better under him
Although it is possible that the final result is not the main goal in a friendly match like this, but by looking at Chelsea's performance in friendly matches against Celtic and Wrexham some time ago we can see that in the end there are still some things that Chelsea must improve in order to support a good performance later.
There are still many mistakes made in cooperation problems which in the end there are not a few mistakes from the players themselves.
In addition, the problem of emotions also seems to need to be taken into consideration and notice from Maresca at this time because after all we can see the tension that occurred when Chelsea faced Wrexham which actually fought on the field was not necessary especially it was a friendly match.
Chelsea still have to be more careful in their development so as not to harm in the season that will run a few more weeks for the EPL.