Has Nadal become too negative?

What's the biggest difference between Roger Federer and Rafael Nadal? It isn't their biceps or their backhands or the state of their knees. It's their respective outlooks on life. Listen to what each had to say at his pre-tournament news conference in Montreal this weekend.

Here's Federer on how he'll stay motivated after breaking the all-time Grand Slam record: "Yeah, it's not a problem. Really, I'm so excited to be back on tour. I've been very motivated, practicing really hard the last few weeks, and that's why I'm back on tour. Otherwise, I would be still stuck at home doing something else than answering questions and practicing and playing matches. But I felt like I was ready to go, I was fresh and in the mood to travel again." Translation: It's good to be me.

Here's Nadal on his ambitions after being sidelined for two months with knee tendinitis: "I have to continue to work on court, and we're going to see in a few weeks, no? Now I'm just here to practice hard and to enjoy playing tennis all the time, and trying to find my best form as soon as possible. [But] here in Montreal, it's going to be almost impossible."

There are good reasons for these two men to have differing attitudes at the moment. It's been a summer of love for Federer; he has won the French Open and Wimbledon and become a father two times over. For Nadal, it's been a summer of pain; he watched from his couch as his rival took those two titles from him and passed him for the No. 1 ranking, all while dealing with his parents' separation. Of course, Federer is going to be happy and positive. Of course, Nadal will be wary of his prospects.

That said, there's one sentiment in these speeches that exemplifies the more significant difference between them. It's the final word of Nadal's quote: "impossible." No matter what the circumstance, that's not something you're likely to hear Roger Federer say. Deep down, wherever he is and however he feels, he believes he should win. It's what gave him the faith, after so many defeats on clay to Nadal, that he could win the French Open someday.

Nadal has always taken a more philosophical and honest-at-all-costs approach to the sport. He doesn't believe he should always win, and while this helps him calm his nerves as he plays and accept defeats when they happen, it may also keep him from reigning for long periods at No. 1 -- if Federer is like Pete Sampras in his easy self-assurance, Nadal is closer to the reflective and at times self-doubting spirit of Andre Agassi, who never thrived when he was on top. Nadal has been schooled in humility and stoicism since he was a kid by his Uncle Toni, and his lack of entitlement has made him an appealing champion. But more recently, it seems that Toni's reflexive pessimism -- before Wimbledon, he said that his nephew was nowhere near ready to play -- has seeped into Rafa's psyche.

For years, Uncle Toni has sung Federer's praises, and Rafa has followed suit, never missing a chance to claim that the man he has beaten 13 of 20 times is the "greatest he's ever seen." Nadal lost his top ranking because of an injury, but there was also a sense that his mind wasn't ready to tackle a defense of Wimbledon so soon after he'd suffered his first loss in Paris. Has Nadal begun to buy into Federer's own attitude, that the Swiss really does belong at No. 1? That's not a recipe for success. After all, the famed slogan of Nadal's biggest sponsor is "just do it," not "it's going to be almost impossible."