LONDON—Rafael Nadal discusses why he feels different playing indoors. The Spaniard has never won the ATP World Tour Finals, but says the hard-court surface is less significant than the playing environment. The court at the O2 arena in London is said to be playing slower than last year.

“I like the sunshine,” Nadal said with a smile. “Is a little bit different. The feeling on the ball, on your racquet, is different. The sound is different. All of these small things that make you feel a little bit strange. I didn’t play a lot on indoor in my career. But is not a thing that I don’t like to play in indoor. I like to play in indoor. But is true that the feeling on the ball is little bit more strange than when you play outside, no? Sometimes I feel like the ball stays less time on the racquet than other surfaces, no? But at the end, is not a big deal. Just the opponents have the chance to hit the ball and to go for the winners with better chances of success than in outdoor courts.”

Nadal added that the surface inside the O2 Arena is slower than the one the men played on last week at the Paris Masters. Nadal lost to David Ferrer in the Paris semifinals, but defeated his compatriot in London.

“I let you know after the tournament if I happy [with the surface] or not. But I really like the fast surfaces. Because of my success on clay, lot of people thinks that I play much better in a slower surfaces. And I think that’s completely not true. I have my best results on hard court are in fast surfaces. I win in Montreal two times. That is one of the fastest. I won in Cincinnati this year. That is one that is very fast. And Indian Wells is not a slow court. Indian Wells, is true is not very quick, is not very slow, and the bounces are always high. Always the easier one for me to play. But Shanghai this year was very fast and I had a great feeling playing there. Is not a question of the speed of the court. Is a lot of different factors make you feel good or bad. The balls are very important sometimes when you play in these kind of surfaces. I am happy. The court is in perfect conditions here.”