MASON, Ohio (AP) -- Top-seeded Jelena Jankovic and second-seeded Caroline Wozniacki were knocked out in third-round upsets at the Cincinnati Women's Open on Thursday.
Qualifier Akgul Amanmuradova used a decisive serve advantage to upset the second-ranked Jankovic 7-6 (2), 6-4, shortly after 16th-seeded Marion Bartoli won eight straight games on her way to beating the third-ranked Wozniacki 6-4, 6-1.
Just one of the top nine seeds - No. 4 Kim Clijsters - and five of the 16 remained alive going into the quarterfinals of the $2 million Western & Southern Financial Group Women's Open.
Sixth-seeded Vera Zvonareva fell to 11th-seeded Flavia Pennetta 6-4, 6-3, while seventh-seeded Agnieszka Radwanska was eliminated by 10th-seeded Maria Sharapova 6-2, 6-3, and eighth-seeded Li Na lost to 12th-seeded Yanina Wickmayer 2-6, 6-2, 7-6 (4).
Also, No. 13 seed Shahar Peer fell to Anastasia Pavlyuchenkova 5-7, 6-4, 6-4.
The seventh-ranked Clijsters easily advanced, ousting No. 132 Christina McHale 6-1, 6-1. McHale, the last remaining American, only had two break-point opportunities and didn't convert either, while Clijsters went 5 for 10.
Sharapova, who is scheduled to face Bartoli in Friday's evening match, believes the rash of upsets can be traced to the balance in women's tennis.
"I think it just speaks a lot about the depth of the game right now,'' said the Russian, who is playing in the tournament for the first time. "I think the depth of the game is a lot deeper than it was, say, a few years ago, where maybe in the first few rounds you could have gotten a few easy matches, easy scorelines. I think now, from the get-go, you really have to be ready for the first round. You're facing really tough opponents, and some of them are not seeded or dropped in the rankings, but to be honest, at the end of the day, that doesn't really matter. You still have to go out there and face them.''
Former No. 1 Ana Ivanovic continued her impressive run with a 6-0, 6-3 win over No. 49 Elena Vesnina. The 62nd-ranked Ivanovic has beaten three higher-ranked opponents to reach the quarterfinals.
The 114th-ranked Amanmuradova, the last qualifier to reach the quarterfinals in 2007, had 12 aces with no double faults, keeping the tournament's defending champion on her heels.
"I didn't expect to go that far,'' said Amanmuradova, who is scheduled to meet Ivanovic in the quarterfinals. "I knew Cincinnati was very strong, being a Premier event for the second year. Last year, I lost in the first round. I was just hoping to pass through the qualifier and see what happens. Today was one of my best games ever. I'd never beaten a top-10 player.
"Serving a lot of aces helped me save my energy,'' she said.
Jankovic played just two matches one week after losing in the first round at San Diego in her first match since injuring her left ankle during the second round of a tournament in Slovenia in mid-July.
"The key to today's match was I really didn't return well, and her serves were really accurate,'' Jankovic said. "I didn't really have many chances. When I had the chances, I didn't really take them. When I was able to hit the return, I would make mistakes. So, unfortunately, I didn't do what I was supposed to do. She was a better player today.''
Wozniacki had won six straight matches and was leading 4-3 in the first set before Bartoli got going and won the last three games of that set and five more to take control.
Momentum changed when Bartoli won a challenge on break point in the eighth game.
"To break her, especially to get this challenging call when the ball was out and the line judge called it in and actually it was out on the break point, it was kind of a huge turning point,'' said Bartoli, whose quarterfinal opponent is Sharapova. "I felt like, after that, I served really well, and it helped me a lot to stay on top today.''
Wozniacki questioned the chair umpire about the timing of Bartoli's challenge.
"I think it was a late challenge,'' she said. "It was a pretty important point, and I felt like she hit the ball and she was playing it, and saw that she hit it out and then challenged.''