Real Madrid must spend some time to calm down from the defeat and try to come back after this shock defeat. They are still have one point less than Barcelona so it is not a too bad standing for them and with a long season, their race with Barcelona is still opening.
Yes, I think this is the first defeat for Madrid at the start of this season, so far they are playing on a winning streak and of course losing this Derby match is certainly not a failure for Madrid, because there is still a lot of time to catch up to win the Laliga title this season. This and even this defeat only made a difference of one point with Barcelona and Girona.
Atletico Madrid seems to know better how to beat Madrid at home, of course they have a lot of experience from each previous meeting, Madrid must recognize Atletico's greatness at home so this defeat must be an important lesson for Madrid so they can play better in the next match against Las Palmas , at least maintaining a safe position in the top 4 of the standings.