A first-leg 3-0 victory sees Real take full control of the round of 16 tie.
At the final whistle, Courtois had a pop at their season critics: "It's difficult, in the end we have a very young team and that's sometimes forgotten.
"I know we're Real Madrid and we aspire to win everything, but it's true that we're still growing, there are a lot of kids, a lot of young players, and things haven't always gone well. I remember in my first year we were much worse off, and for me there wasn't this somewhat toxic atmosphere, in quotes, where everything is considered terrible, awful, and when you lose you hit rock bottom.
"It's true that we've had an up-and-down season, but for me, the biggest lack of respect is towards the dressing room, saying that we're not professional, that we asked not to play in Albacete, that we have more power than the manager. I think that's wrong because we are professionals and we do what the manager asks of us.
"We're not there saying, 'Well, we don't feel like training today.' Obviously, that doesn't exist; we're Real Madrid and those things don't happen here, but sometimes these things come out and create a toxic atmosphere with the fans who think we do whatever we want."