Chelsea goalkeeper Petr Cech is reportedly close to the end of his career after an array of injury problems.
The 29-year-old, who missed three weeks of the season due to a knee problem, suffered a major injury five years ago when he fractured his skull in a collision with Reading's Stephen Hunt.
The Blues' 19-year-old goalkeeper Thibaut Courtois believes that the Czech Republic international may not have much time left playing in the Premier League.
"I know [Cech] has problems in his knees and on his back," Courtois told Spanish radio station Onda Cero.
"Chelsea's goalkeeping coach told me he doesn't know how much time Cech can play at the top level."
Courtois, who is currently on loan at Atletico Madrid, joined the London side from Genk this summer.