Chelsea have agreed a deal to sign the highly rated young goalkeeper Thibaut Courtois from the Belgian champions Genk, André Villas-Boas has confirmed. Reports suggest the fee could be as much as €9m (£7.9m).

"There is an agreement between the two clubs," the Chelsea manager said. "It is also subject to personal agreements and from then we will decide what is best for him."

Genk announced in a statement on their website that they were left with no option other than to let the 19-year-old leave when he did not appear for Saturday's friendly against Lyon. They said Chelsea's offer was "by far the largest bid" they have ever received for a player.

The 6ft 6in Courtois was the first-choice goalkeeper for Genk last season. He also received a first call-up to the senior Belgium squad, but is aware breaking into Villas-Boas's team will be a much tougher proposition.

"Chelsea see me as the successor to Petr Cech," he said recently. "It won't happen in one or two years, but in three, four or five years. I can therefore work on my development in peace."

Chelsea could immediately loan out the teenager – who had also been linked with Atlético Madrid as a replacement for David de Gea – to give him more experience.

Asked about Courtois's prospects, Villas-Boas added: "Let's wait for him to agree terms. It seems unfair for me to make any comment on him but as soon as he is a Chelsea player we will see what kind of future he has."