Cech has been Chelsea's first-choice keeper since joining the London club in 2004, but the Czech Republic international has come in for criticism after an error in Wednesday's 3-1 UEFA Champions League defeat to Paris Saint-Germain.
The 31-year-old allowed a near-post effort from Javier Pastore to sneak into the bottom corner late on, leading some to question his place in the side.
And Cech's position as starting goalkeeper could soon come under threat when Courtois returns from his third year on loan at Estadio Vicente Calderon at the end of the season.
Belgium shot-stopper Courtois has developed a reputation as one of the top goalkeepers in the world at Atletico, where he has won the UEFA Europa League, UEFA Super Cup and Copa del Rey.
But Cech does not feel threatened by Courtois.
"If, on the first day of pre-season, Thibaut Courtois is here, he is here," Cech told the Daily Mail. "If he is not, he is not.
"It does not change anything. I will still have to do better than whoever else is here, to keep my place. It doesn't change anything for me.
"You could ask John Terry or Gary Cahill about the very promising French central defender (Kurt Zouma) bought by the club.
"If he comes back and he's better than me, credit to him, well done to him, but who knows? I'm not afraid. I'm not a fool to think I've been here 10 years and I'll be here another five, just because.
"I am not playing because my name is Petr Cech. I'm playing because I've been playing well and because the manager thinks it improves the team with me in goal.
"I've never had a manager who would just put me in the goal because everybody was used to seeing me there.
"Are you good? Are you not? I'm not crazy to think in another 10 years I will just be playing.
"There will come a day when somebody comes along who is better than me. That's it. But my everyday fight is to avoid that as long as I can. This is football life. Let's see."
