Rafael Nadal can count himself unfortunate to lose the top spot, as he has yet to drop a set in the tournament. It was impossible, though, to look past Federer's outstanding display at Rod Laver Arena, where he lost only three games in the match against Del Potro.
Elena Dementieva takes her place - and the two women will square off in Thursday's first semifinal.
1. (2) Roger Federer: Magnificent in quarterfinal and looks as good as ever. SF: vs. Andy Roddick.
2. (1) Rafael Nadal: Still hasn't dropped a set and is enjoying the hot conditions. SF: vs. Fernando Verdasco.
3. (3) Fernando Verdasco: Spanish iron man could find Nadal too much to handle. SF: vs. Rafael Nadal.
4. (8) Andy Roddick: Best Slam performance in two years after a winter of hard work. SF: vs. Roger Federer.
1. (2) Elena Dementieva: Olympic champion will like her chances of a first Slam title. SF: vs. Serena Williams.
2. (1) Serena Williams: Fortunate to survive a poor quarterfinal and must improve form. SF: vs. Elena Dementieva.
4. (3) Dinara Safina: Survived a tough quarter and must fix serving demons on big points. SF: vs. Vera Zvonareva.