Sevilla defense was the main factor in Real Madrid failure to win. Real Madrid had several good opportunities but Sevilla defenders played very disciplined and were always alert in blocking Real Madrid attacks. Real Madrid attack line also didn't play optimally, they wasted several opportunities that could have been goals.
Sevilla success in holding Real Madrid to a draw was due to good play from Sergio Ramos and his colleagues who guarded Sevilla defense area. Real Madrid has tried hard to get an additional three points, but Sevilla managed to make Real Madrid lose two points in this match which made the competition at the top of the standings even hotter.
Sergio Ramos knows very well the strategy that Ancelotti will implement and has proven that he is able to make it difficult for Real Madrid's front line to score goals. He also made a number of saves in this match and it is true that Sergio Ramos is still the best defender at the moment, even though he is no longer young and the pressing intensity is no longer the same as in previous seasons. Sevilla's defense was so solid and neat that they were able to break down a number of opportunities which Real Madrid is trying to build and even though statistically Real Madrid really dominates the match.
Rodrygo had several good opportunities in front of goal to score, but his lack of finishing meant these opportunities were wasted. This is the worry that Ancelotti actually needs to be aware of because when Jude Belligham is unable to score a goal it will have quite an impact on the result of the match.