The 26-year-old stopper left Chelsea on poor terms this summer after he declined to report for training at Cobham in order to force through the move.
And his reputation in West London is unlikely to improve any time soon with his latest comments about his former side.
In an interview with Belgian paper Het Nieuwsblad, Courtois spoke about the difference between his current and former clubs whilst taking a not so subtle dig at the Blues.
In training, you see that the level is high. I am now experiencing on a daily basis that Sergio Ramos is the best centre-back in the world. The level [at Real Madrid] is higher than at Chelsea.
[The Santiago Bernabéu] is twice as big [as Stamford Bridge], of course, it's a very different feeling.
If you look forward you only see a wall of people, while at Stamford Bridge you can still see the sky or the hotel behind the grandstand.
The Belgium international had already irked Blues fans by kissing the Real badge as soon as he was unveiled by the Spanish giants last month.