PARIS -- Novak Djokovic's physical improvements, through rigorous diet and diligence in the gym, have drawn a great deal of attention. Less obvious and far harder to quantify are the strides he has made in the department of mental health.
This might be the most important, if overlooked, factor in Djokovic's streak of 41 victories to start 2011.
"It's really a requiring sport," Djokovic said after his fourth-round victory over Richard Gasquet. "You have to travel and play so many matches on different surfaces, different continents, different countries. It really is a mental game.
"You try to have the emotional stability every day, because tennis has the longest season in all sports."
That was Sunday, before the 24-year-old Serb learned that Fabio Fognini, citing a torn muscle in his thigh, was going to take a pass on their quarterfinal match. That meant Djokovic would have four days off before his semifinal meeting with the winner of the contest between Roger Federer and Gael Monfils.
These four days have already been the subject of animated debate. Even the players have been engaged.
"I don't think that's a good thing for him, honestly," said Ivan Ljubicic, who is a good friend of Djokovic's. "I think at this stage to have four days off without competitive matches, it's not easy, it's not good. And especially for him, probably the biggest match of his career coming up, playing for the No. 1 spot against probably Roger Federer. It's not going to be easy for him."
Rafael Nadal, whose No. 1 ranking Djokovic will be playing for, isn't buying that analysis.
Rafa, who turns 25 on Friday and is starting to sound like an old man, was asked what his reaction to four days off would be.
"Fantastic, no?" Nadal said, drawing laughter. "Tell me what's the worst part of that?"
He seemed amused when the journos here told him that Ljubicic was worried about Djokovic's rhythm.
"After don't lose a match during all the year with, I don't know, 40-something straight victories," Nadal said, "you think he's out of rhythm now?"
No, Djokovic should be fine physically. But now, more than ever, we will see how far he has evolved on the mental side.
He finds himself on the cusp of all the things a tennis player desires: The No. 1 ranking and a place in the final of a major. And then there is the streak of 41 match wins. To win the title here -- it would be the third of his career -- he may well have to go through Federer and Nadal, who have been the standard in men's tennis for nearly eight years.
Four days. Ninety-six hours:
Breakfast. Lunch. Dinner. Training. Practice. Massage. Shower. Transport. Texting. Tweeting. Surfing the Internet. Socializing. Sleep. And then do it all over again. And again. And again.
There is a lot of time in between those diversions to think. An eternity for Djokovic to ponder his destiny.
Greg Garber is a senior writer for ESPN.com.