After three seasons on loan at Atletico Madrid, the 22-year-old Belgium goalkeeper has returned to Stamford Bridge and taken the place Cech has occupied for a decade.
Courtois has two years remaining on the contract he signed when moving from Genk in July 2011, with an extension close.
“It’s not yet signed,” said Courtois. “When I am back at Chelsea I will probably sign the new contract.”
Courtois added: “We don’t talk about the situation, but of course I know he (Cech) has played 10 years at Chelsea and that now I am playing and for him it’s not the nicest situation. But that is the decision of the board and the trainer.”
Meanwhile, striker Diego Costa has withdrawn from the Spain squad for their European Championship qualifier with Macedonia with a hamstring injury.
The 25-year-old has been hampered by similar problems for the last four months and had to limp out of Spain’s friendly defeat by France on Thursday.