Chelsea versus Real Madrid fixture is definitely a 50-50 chance but I am going to lean towards the side of Chelsea mainly because they are seems to have inculcate the winning mentality in the team even at the face of adversity, they have been playing well and winning games as if the club is not under pressure from the government and football organizations. I doubt if Real Madrid team is as strong mentally as Chelsea.
What is your reason to doubt Real Madrid mentality? If we are talking about the mentality of Real Madrid, they must be superior to Chelsea. You can count yourself how many times Real Madrid can come back from behind in UCL matches, even some of them in the final UCL. They have enough experience to deal with the pressure in UCL competition, they surely have a winning mentality. In reality, they prove it by leading the number of UCL titles till today. So, no reason to doubt with Real Madrid mentality. What we need to suspect how is the physical health of each player ahead of the match. The team that can release all their key players and has no problem with injury, should be the favorite to win.