This was a case of actions speaking far louder than words, and the way things slipped away, so suddenly and stunningly, Sharapova clearly was flustered — by the swirling wind and bright sun, by her errant strokes and, most of all, by the Krakow Kid across the net who kept moving way up to receive serves.

Sharapova reeled off eight consecutive games to go up a break in the third set, then dropped the final six games and lost 6-4, 1-6, 6-2 to 18-year-old Agnieszka Radwanska of Poland in the third round, the earliest exit by a No. 2-seeded woman at the U.S. Open since 1981.

"I don't know if it was a combination of the circumstance or the wind or the opponent playing well. I don't know what it was," said Sharapova, who double-faulted a whopping 12 times. "I just didn't quite feel like me out there."

The braces-wearing, big-hitting Radwanska isn't exactly a nobody. She won junior championships at the French Open in 2005 and Wimbledon in 2006, took home her first tour title this month and came to New York seeded 30th. Still, she understood the circumstances Saturday.

"I had nothing to lose. She was the favorite _ and I think she was more nervous," said Radwanska, who will fulfill a prematch promise to her younger sister, this year's Wimbledon junior champion, by buying them matching Louis Vuitton handbags to celebrate the upset.

She wasn't the only 18-year-old from Eastern Europe who pulled off a big win Saturday: Victoria Azarenka of Belarus beat 1997 champion Martina Hingis 3-6, 6-1, 6-0, and Agnes Szavay of Hungary eliminated No. 7 Nadia Petrova 6-2, 6-3. Plus, 16-year-old Tamira Paszek of Austria knocked off No. 11 Patty Schnyder 4-6, 6-4, 7-6 (1). All of which means 2004 U.S. Open champion Svetlana Kuznetsova has to like her chances in the bottom half of the draw.

"You can see the new generation coming up," Hingis said. "They're very dangerous. I knew it's not going to be easy. My mom texted me. She said, 'Watch out.'"

Sharapova had lost a combined two games in her first two matches, but could have used some similar advice before facing Radwanska. If that was the most surprising result of the tournament so far, what happened later in Arthur Ashe Stadium almost would qualify: Three-time reigning men's champion Roger Federer lost a set against 6-foot-9 American wild-card John Isner, who only a few months ago was leading Georgia to the NCAA team title.

For one glorious set, the 184th-ranked Isner stayed right with the man who's been at No. 1 for a record 187 straight weeks. And when Isner ended a 13-stroke exchange with a big forehand approach shot, then smacked service winners at 134 mph and 124 mph, he took that first set in a tiebreaker.

Isner punched the air and strutted to the sideline chomping on his white towel, while his supporters, some in Georgia Bulldogs regalia, jumped and yelled and barked their approval. The partisan home crowd rose, too; pretty much the only people in their seats at the ensuing changeover were the family and friends in Federer's guest box.

Remember: Federer has won 11 Grand Slam titles, while Isner has played in three Grand Slam matches, all this week.

"Four months ago, I was unranked," Isner said. "To go from that to beating Roger Federer in a set is pretty cool."

And was going through Federer's mind at that moment?

"I'm thinking, 'This could be a really difficult match from now on. I knew it from the start, but now I have proof.' I was worried," Federer acknowledged.

And then, nearly as quickly as Sharapova came unraveled, Federer came together. Remarkably, he did not make an unforced error _ not a single one! _ during a 105-point stretch that included the entire second and third sets in his 6-7 (4), 6-2, 6-4, 6-2 victory.

Federer even conjured up a lob that curled over the second-tallest man on tour and landed in a corner.

"Doesn't happen every day," said Federer, trying to become the first man since the 1920s to win this tournament four years running.

He set up a fourth-round meeting against Feliciano Lopez, who ended the run of 18-year-old Donald Young of the United States by winning in four sets. The Federer-Lopez winner will take on the winner of No. 5 Andy Roddick vs. No. 9 Tomas Berdych in the quarterfinals.

One minor upset came when No. 19 Andy Murray lost to 43rd-ranked Lee Hyung-taik 6-3, 6-3, 2-6, 7-5. Lee, in the U.S. Open's fourth round for the first time since 2000, will meet No. 4 Nikolay Davydenko, who defeated No. 28 Nicolas Almagro.

Roddick, the 2003 U.S. Open champion and runner-up to Federer last year, zoomed 19 aces and zipped past 2002 Australian Open champion Thomas Johansson 6-3, 6-2, 6-0, then explained to the crowd, with a wink and a smile, why he was in a hurry.

"I've got to try to find myself a hot date later," said Roddick, who's dated actress Mandy Moore and been linked to Sharapova in the past, "so I tried to get off the court a little faster."

He's spoken about being pleased to see other U.S. men making strong showings, taking some of the attention away. His Davis Cup teammate, No. 6 James Blake, was to face Stefan Koubek at night, but Young and Isner couldn't keep pace on this day.

"The difference between that pressure and the pressure I have," Roddick explained, "is they lose and it's OK, you know?"

His next opponent, Berdych, is best known for upsetting Federer at the 2004 Olympics, and advanced Saturday with a 7-6 (2), 6-1, 7-6 (3) win over Fernando Verdasco.

Now Radwanska has her breakout moment, and she did it despite looking quite bad in the middle of the match.

"She destroyed me in the second set," Radwanska said. "But then I woke up."

Said Sharapova: "You'd think I'd have the momentum."

She always appeared bothered by one thing or another. She started the match without a visor, then added one. She tried to wait out wind gusts before serving, then would catch her toss anyway.

And then there was what kept happening before Sharapova's second serves. Radwanska would walk halfway to the service box and stand there, before hopping in place and then shifting back some. It was not only a tactic, but also basically an insult, akin to saying, "Hey, Maria, I'm not intimidated by your serve in the least."

Sharapova insisted afterward that didn't rattle her _ "I usually don't think about where my opponent's standing," she sniffed _ yet three were all of those double-faults.