The goalkeeper, who has spent the last three seasons on loan to Atletico Madrid is due to return to Stamford Bridge this summer and fight for a first-team place with Petr Cech.
Courtois, 22, has been linked with a permanent move to Atletico in recent weeks but Jose Mourinho has insisted that the shot-stopper will return to the west London club.
And asked about Courtois’ situation, his Belgium team-mate Lukaku replied: “I don’t know, I only read about it. You’ll have to ask him.
“I think it’s time. He’s played at a very high level in Spain for three years. It’s time to see him in England.”
Speaking last week, Mourinho said: “When the World Cup in Brazil is over, Courtois will be coming straight back to Stamford Bridge – end of story.”
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news