NEW YORK -- Kaia Kanepi found there is such thing as being too aggressive.
The Estonian climbed to 18th in the world in May 2009, then tumbled to 140th less than 12 months later. She lost in the first round at 11 straight tournaments at the end of last year.
But just as quickly as she lost her form, Kanepi has regained it. Her sizzling summer continued Saturday when she upset fourth-seeded Jelena Jankovic in the third round of the U.S. Open.
The 31st-seeded Kanepi won 6-2, 7-6 (1) at blustery Arthur Ashe Stadium. It was just her second win in 10 tries against opponents ranked in the top five.
"Last year I just started losing and losing and the confidence went down and I didn't know what to do," she said.
What she did was focus on becoming more patient. Kanepi had 19 winners and 37 unforced errors in the difficult conditions Saturday, compared with 13 and 41 for Jankovic.
"I'm still aggressive but not that much and not with every shot I hit," Kanepi said.
Kanepi advanced to the fourth round at the U.S. Open for the first time. She had to go through qualifying just to play at Wimbledon, then reached the quarterfinals. At Palermo in July she became the first Estonian woman to win a singles title.
The 25-year-old has moved up more than 100 places in the rankings since May 10.
Jankovic reached her only Grand Slam final at the U.S. Open in 2008, but she lost in the second round last year. The Serb struggled with the wind Saturday, at one point hitting a serve so badly the ball flew straight up into the air.
"I had a hard time serving," she said. "You toss the ball, and it was all over the place. And then you hit the ball one direction, it goes another. You're just getting ready to hit the ball and just moves away from you. So it was really hard out there. But she handled the wind a lot better than I did. She was the better player today."
Kanepi can't stand the wind, either. But on a day when both players took turns venting their frustration, she made the fewer mistakes. She had a chance to serve out the match in the second set but was broken. In the tiebreaker, though, Kanepi had no trouble closing out the victory.
"I don't think it was because of the wind at 5-3," Kanepi said. "I think it was because of the head."
As a young tennis player, Caroline Wozniacki admired a Russian star for her glamorous image off the court.
Sorry, Maria Sharapova, it wasn't you.
"Well, to be honest, Kournikova was always for me the girl that I wanted to be like her," the U.S. Open's top-seeded woman said after she advanced to face Sharapova in the fourth round.
"I thought she was very pretty; she was handling everything really nicely. You saw her everywhere in the commercials. I think I would more go for Kournikova."
Wozniacki and the 14th-seeded Sharapova lost one game between them in straight-set wins Saturday in the third round. That sets up a tantalizing matchup pitting a three-time Grand Slam champion seeking to prove she's all the way back from injury against a 20-year-old chasing her first major title.
Anna Kournikova, of course, never won a Grand Slam singles championship. So Wozniacki looked up to other players for on-court inspiration. Sorry, Maria, it was Steffi Graf and Martina Hingis.
Rafael Nadal's third-round opponent at the U.S. Open, Gilles Simon of France, got his wish: an afternoon match Sunday, rather than a night match.
Simon had a son born Thursday back home in Europe, and he's eager to go see the baby. After winning in the second round, Simon said he hoped he would face Nadal during the day, so that if he loses, he can make it to the airport in time to catch a flight. Playing at night wouldn't have allowed that.
When Simon's concern was relayed to Nadal, the U.S. Open's top-seeded man said: "Really? If he wants, I'll buy him the tickets."
Simon and Nadal -- whose first two victories in the tournament both came under the lights at the end of the day -- were scheduled for the third match in Arthur Ashe Stadium on Sunday, when play starts at 11 a.m.