Real Madrid goalkeeper Thibaut Courtois says they must not underestimate Chelsea tonight.

Chelsea host Real in the second-leg of their Champions League quarterfinal needing to overcome a 2-0 deficit.

Former Blue Courtois said: “They have players of a world level who are able to achieve success — although I hope the bad run continues on Tuesday. We are obliged to play very much with our heads and to forget the advantage we have from the Bernabeu.

“The team is prepared for a difficult match in London. Chelsea maybe in crisis in terms of their points in the Premier League but they are always a difficult rival.

“There doesn't exist an easy English rival. Chelsea have an obligation to attack as they search for a goal and maybe that means we can manage the situation better.

“We hope for a tactical match not a crazy match from the first minute."

Courtois added: “People speak about a semi-final between City and Real but in this moment nothing is resolved. Real Madrid still aren't in the semi-final of the Champions League yet — the score is positive but not decisive.

“Anything can happen in 90 minutes of football and especially against an English club in England. The key for the match will be to control the ball for much of the time and not let the Blues create in our area.

“The longer the game goes on and Chelsea haven't scored, we are much further on our way to success."