Rafael Nadal has always been the favorite in matches at Roland Garros, except for a handful of occasions in the past.
One of the primary reasons is, of course, the surface. A clay court is like his own playpen, and he has that intimidation factor when he is playing on it. Add to the extra space behind the baseline that he's afforded because of the size of the main court at the French Open, and it's almost impossible to hit through him.
This explains why he has only lost three matches since 2005 and won the title on a record 13 occasions. But one other important factor pertains to the scheduling. We know that the French Open has instituted a night session since the construction of the roof on top of Philippe Chatrier.
The conditions are drastically different in the evening, and the legendary Spaniard openly admitted his dislike for playing at night because the ball can be heavy and slow.
What it does is make his potent forehand less impactful, which makes his opponents more rally-tolerant. It's even a bigger problem when the opponent on the opposite side of the net is Novak Djokovic, who doesn't mind playing longer rallies.
The Serb is also the healthier of the two right now, given Nadal's foot problems. Nadal's quarterfinal match against Djokovic is the most anticipated match at the tournament since the draw was made almost two weeks ago, and it has been confirmed that it will be a night session.
Djokovic has previously stated about his preference for playing at night. Last year, he defeated Nadal in the semifinal in a match that finished past the evening hours. Alex Corretja briefly commented on the Eurosport news.
"Oh dear! We will have time to talk about [the conditions]. Of course Rafa’s game is not as effective because usually he likes to hit the ball with a lot of spin, meaning that the ball will go very high. But if he plays at night, the ball might bounce a little bit lower, and for Novak’s game, [that is] better. Obviously the conditions are the same for everyone, but it depends on your game. It can suit your game more or less, and that’s why for Rafa’s game, it is always better when it’s sunny."