The Real Madrid goalkeeper has declared he's ready to return to international football after falling out with Garcia's predecessor Domencio Tedesco last year.
Courtois turned down all efforts from the Federation to end the rift. However, he is now set to return after Tedesco was sacked and replaced by Frenchman Garcia.
In response, Belgium and Al-Qadisiya goalkeeper Casteels says he'll quit the national team if Courtois returns.
He said on a local podcast: “As of today, I am not available for the national team,.
“First of all, it seems a bit strange to me that Courtois can decide for himself whether he wants to return. And it seems strange to me that the federation changes its mind in this way and rolls out the red carpet for him and welcomes him with open arms, as if nothing had changed.”
He continued, “It is not so much about Thibaut, but above all about the football federation. It does not fit with the standards and values that I consider appropriate for a team or sports organisation."