Chelsea quality in the Premier League in the last few matches has been very entertaining, but Chelsea must be careful when dealing with Real Madrid in the Champions League. Real Madrid will be very dangerous when they have the ball. Real Madrid will turn into a savage wolf who can kill the opponent's game because they have a lot of quality. They have proven when dealing with PSG and facing Real Madrid is a tough job for Thomas Tuchel.
The probability of Chelsea winning against Real Madrid in my opinion is much better in the first leg. Chelsea are playing at home and that should be the reason why they will be favorites to win over Real Madrid.
I don't think Real Madrid are far superior to Chelsea this season. Real Madrid's defense is not good, their midfield is not as good as a few seasons ago and they only rely on Benzema as a goalscorer. You will probably know that there will be a tight guard for Benzema in that match if he is really available, and that man-marking strategy will get Real Madrid in trouble.
Real Madrid to me has two challenges that may cost them the champions league qualifications against Chelsea. One of the challenges is Benzema availability. If Karim Benzema is not available for the game, Madrid is obviously gonna struggle. Secondly is the team of Madrid is filled with old men but experienced. Kroos, Modric and Casimero are too old and becoming weak. But Chelsea is rather parading young players that has the ability to bully any player. In terms of strength, Chelsea has it better than Madrid. So, there's also a good chance for Chelsea to qualify.
Real Madrid played 2 hopeless games against Chelsea last season. I seem to remember that once they lost without a chance, and that the other match ended in a draw. Admittedly, that Madrid team had a kind of form crisis at the time. They obviously got a huge boost from that win over PSG. That was great after that 0-1 deficit. I currently rate Real Madrid slightly higher than Chelsea, but these are games that can fall in all directions in terms of results.