Real Madrid could suffer their first defeat of the season in that match but I doubt it and I think the worst result for the away team is a draw, not really sure about the score, if it's a draw then 1-1 or 2-2.
Atletico Madrid league form has not been really promising and likewise Real Madrid; their form is good but there are no goal scorers in their squad. i believe its either a 1-1 draw or a Real Madrid 1 nil victory in the Madrid derby
Atletico faced decline on its mentality after it was getting lose against valencia. It was also getting draw against lazio in UCL. Madrid sees upcoming match as an opportunity for the club to get full points. I think that the possible result will be draw.
Madrid may also show another surprises like when it was scoring when the game was coming to its end. Atletico madrid needs to be careful with bellingham as a guy with some magic.