"When you change a manager there is always the atmosphere that you never know what is going to happen," Cech told Chelsea TV.
"There is a new man coming in, he has got other ideas, so some people might play, some might not - so it is always difficult to deal with.
"Everyone has to deal with this individually and as a group. Everyone needs to be together and try to move on and focus on football, which is not easy to do."
"At a club as Chelsea is, you need to impress the manager every day," the Czech Republic international added.
"If you don't perform well in the training sessions or you don't work hard to show your manager you are ready for the game, you are at the same risk as when a new manager comes in.
"You have to keep working and show you deserve the place in the starting XI and that is basically the life in the big clubs."