Andre Agassi, the only American, man or woman, left in the draw, is also the only man remaining in the tournament who has not dropped a set. Does that means he's playing too tough or he's yet to be challenged? The answer may come when he takes on former U.S. Open champion Marat Safin in the semifinals on Thursday (ESPN 2 p.m. ET).
While Agassi, always one of the fittest players at this time of the year, has fresh legs, Safin cannot say the same. Safin hasn't played one match in less than four sets, and he's fresh off a five-set battle with Andy Roddick.
In a news conference, Agassi assessed his opponent's weapons.
"Big serve. That worries me. 6-(foot)-5 always tends to worry me a little bit," Agassi said. "Monster forehand is a bit concerning as well as a backhand that he can crush both directions, and the fact that he moves well is a bit unsettling."
Agassi owns the head-to-head record at 3-1. Their last meeting was in Lisbon in 2000 with Agassi winning 6-3, 6-3. Since then, Safin suffered through a sophomore slump after winning his first major in 2000 and then was injured throughout most of last year. Safin does have a tendency to lose his patience on the court, frequently earning fines for racket abuse. Agassi's the type of player who tries an opponent's patience, and legs, by sending him side-to-side and back again, earning Agassi the nickname The Punisher.
Potential show stoppers
The biggest question on the women's side is whether Kim Clijsters' ankle will hold up. She turned it again in her quarterfinal and there's no rest day before her semifinal. This will be her third consecutive appearance in the semifinals of the Australian Open. Her opponent, Patty Schnyder is quite familiar as they met three times last year with Clijsters winning in straight sets every time.
It's been four years since No. 1 seeded Justine Henin-Hardenne played Fabiola Zuluaga. Henin-Hardenne beat the Colombian 6-4, 4-6, 6-2 on a hard surface.
Zuluaga, 25, is carrying the standard for her country as the first Colombian to ever reach the semifinals of a Grand Slam event. She's a baseliner who prefers playing on clay courts.
Cynthia Faulkner is the tennis editor for ESPN.com.