Tennis superman Roger Federer looked like a mere mortal on Monday, but Switzerland's world No. 1 still found a way to claim a three-set victory over Mariano Zabaleta in the third round of the ATP Masters Series tournament at Key Biscayne.
Federer won his 18th straight match but looked far from invincible in a 6-2, 5-7, 6-3 victory over the unseeded Argentinian on a windy night on stadium court.
"To be on top in the end, I'm really, really satisfied, because it was tough out there," Federer said.
The top seed, winner of four tournaments already this year but in search of his first Key Biscayne crown, appeared on his way to a routine straight-set win when he broke to lead 5-3 in the second set.
But Zabaleta, ranked 52nd in the world, wasn't ready to go down without a fight as he broke Federer to launch a run of five straight games for the set.
Once in the third set, Federer said, everything was harder.
Federer certainly didn't look comfortable in the third, failing to convert break chances in the second and sixth games before finally breaking the Argentinian with an overhead to lead 5-3 and serving out the match.
In the fourth round, Federer will face Croatian Mario Ancic, who beat 16th-seeded German Tommy Haas 6-4, 6-4.
While Federer was able to hang on, fourth-seeded Argentinian Guillermo Coria couldn't.
Coria, runner-up to Andy Roddick here last year when he retired from the final with back spasms, fell to American Taylor Dent 6-3, 6-4.
He followed second-seeded Roddick, third-seeded Australian Open champion Marat Safin and fifth-seeded Spaniard Carlos Moya out of the draw.
The tournament still boasts favorite son Andre Agassi, a six-time champion here who posted a business-like 6-2, 6-4 over French qualifier Arnaud Clement.
"I felt really settled from the beginning," Agassi said.
"I was very comfortable sort of hitting a quality ball that I knew I could hit over and over again in tough conditions," he said.
Agassi next faces French Open champion Gaston Gaudio of Argentina, the seventh seed, who beat France's Sebastien Grosjean 6-2, 6-3.
Briton Tim Henman, the sixth seed, also advanced, with a smooth 6-3, 6-1 triumph over Argentina's Juan Ignacio Chela.
Women's top seed Amelie Mauresmo, seeking her second title of the year after a triumph in Antwerp, reached the quarterfinals here for the first time in four appearances with a 6-1, 7-5 victory over 16th-seeded Croatian Karolina Sprem.
Second-seeded Russian Maria Sharapova, the reigning Wimbledon champion, also advanced with a 6-1, 6-2 victory over Japan's Shinobu Asagoe.
But two other Russian Grand Slam champions, Anastasia Myskina and Svetlana Kuznetsova, were ousted.
Myskina, the fifth seed, had the misfortune to come up against former world No. 1 Kim Clijsters, fresh from a triumph at Indian Wells, California, that heralded her return from a year battling a wrist injury.
Clijsters, unseeded since her world ranking has yet to catch up with her comeback, defeated Myskina 6-3, 6-4.
Unseeded Serbian Ana Ivanovic, just 17 years old and ranked 52nd in the world, upended sixth-seeded Kuznetsova 6-3, 3-6, 7-5 to book a clash with Mauresmo.
Clijsters will take on another Russian seed, No. 4 Elena Dementieva, a 3-6, 6-2, 6-1 winner over France's Tatiana Golovin.
Sharapova will face another Belgian former world No. 1 currently on the comeback trail, Justine Henin-Hardenne, who beat seventh-seeded Australian Alicia Molik 6-4, 2-6, 6-2.