The 2009 TIME 100

I have never seen such tenacity, such ambition, such fight and such honor go into every shot as when I watch Rafael Nadal.

I want to be like him. The attitude he exudes the moment he walks out on the court is the attitude of a true champion. A champion whose desire to win is the same as the desire of a lion to eat. Stalking his prey with force and speed, Nadal, 22, has already become one of the game's all-time best.

What is so unusual about Rafa (which is what he likes to be called) is that unlike many of his fellow Spaniards, he can dominate on all surfaces. He has never lost a match on the French Open's clay, but he also has a Wimbledon title to his name, as well as one from the Australian Open. This year he's the only man able to go for a true Grand Slam.

What makes him so good? I think it's that he's the hardest worker. The last one to leave the court, the first to arrive. The one who falls asleep studying, the first to rise. It's not easy being a champion; you don't just wake up and — bam! — you're No. 1. It takes work, effort, desire, dedication — all qualities that Rafa has. I could be wrong, but I don't think I am far off.

Williams, whose memoir On the Line comes out in September, has won 20 Grand Slam titles