Venus Williams battled past French Open champion Francesca Schiavone 7-6(5) 6-4 in a late-running daytime quarterfinal, while defending champion Kim Clijsters prevailed against French Open runner-up Samantha Stosur 6-4 5-7 6-3 at night.

After two breaks apiece it came down to a tie-break in the first set of the Williams vs. Schiavone encounter, played in windy conditions. The Italian, seeded sixth, recovered from a 0-4 deficit in the tiebreak, but two forehand errors at 5-5 handed Venus the set. The American third seed took control early in the second set but she twice let breaks slip before dismantling Schiavone’s serve once again to win the match. Williams has now defeated Schiavone in all of their eight meetings.

In the other quarterfinal of the day, Clijsters extended her US Open winning streak to 19 matches, which includes her titles in 2005 and 2009 (before and after her retirement). The fifth-seeded Samantha Stosur made the better start but Clijsters fought back to take the first set. Stosur revived in the second set and Clijsters was in trouble in the decider as she was broken three times in a row. In that same set, however, Stosur did not hold serve once. The scrappy match featured a total of 15 breaks.

Williams and Clijsters will face each other in the semifinals and both are chasing their third titles at the US Open.  The two met last year in the fourth round when Clijsters won with an interesting score 6-0 0-6 6-4. (sources: BBC, Women Who Serve, photo: © Neal Trousdale)

Dominika Cibulkova reached her second US Open quarterfinal in two years by upsetting eleventh seed and 2004 champion Svetlana Kuznetsova in the fourth round. Later, top seed Caroline Wozniacki recorded one of the most significant victories of her career by defeating Maria Sharapova for the first time and by building on the momentum gained in the previous three rounds of the US Open in which the Dane lost a total of just three games. The two winners will face each other in the quarterfinals.

Despite a fragile thigh and being down in both sets, the world No.45 Cibulkova defeated Kuznetsova in straight sets, 7-5 7-6(4). The Slovakian could have finished the match earlier, as she served for the second set at 5-3, but Kuznetsova saved two match points and the set went to a tiebreak. The Slovakian didn’t let her opportunity slip away and won that tiebreak to deny Kuznetsova her 101th Grand Slam victory. During the match Kuznetsova made 42 unforced errors and double-faulted 10 times.

Here’s what Cibulkova said afterwards:

I was really pumped for this. I knew I could make it and that I could beat everybody in this tournament. I still feel like that.

The fourth round match between last year’s US Open runner-up Wozniacki and 2006 US Open champion Sharapova was highly anticipated, partly because it was a big test for Wozniacki’s great form but also a big test for more established Sharapova, and the two didn’t disappoint, providing tennis fans with big-hitting contest.

Both Wozniacki and Sharapova had very low break point conversion percentages – Wozniacki just 25% (converting 3 of 12 break points), and Sharapova just 11% (making use of only 1 out of 9 break points). Sharapova also had much more double faults and unforced errors than Wozniacki – nine double faults to Wozniacki’s three, and 36 unforced errors to Wozniacki’s 10. Final match result: 6-3 6-4.

Wozniacki has won the last four meetings against her next opponent Cibulkova, dating back to 2008, and all of them were on hard courts. The Dane is now more than ever a serious contender for a Grand Slam title, and if the repeat of the last year’s final with Kim Clijsters materializes, Wozniacki will be much more likely to go all the way. (photos: © Neal Trousdale)

In the Kim Clijsters vs. Ana Ivanovic fourth round US Open encounter all eyes were on Ivanovic as she was supposed to show that her confidence and form really are back. However, the Serb fell to the Belgian defending champion 6-2 6-1 in just 59 minutes.

After taking the first set, Clijsters raced to a 4-0 lead and soon wrapped up the match in which Ivanovic held serve only once. The former world No.1 Ivanovic admitted that the nerves crept in again and all we can hope for is that it was just a temporary failure in her recent improving form.

Venus Williams was challenged by Shahar Peer in the first set of their fourth round match, but the American had an easier time in the second set to win 7-6(3) 6-3. The third-seeded Williams will next face French Open champion Francesca Schiavone, who defeated Anastasia Pavlyuchenkova 6-3 6-0 to reach her first US Open quarterfinal since 2003. (photo: © Neal Trousdale, sources: Ana Ivanovic's official website)

Top seed Caroline Wozniacki has lost a total of just three games to advance to the fourth round of the US Open. In the first round the last year’s runner-up defeated Chelsey Gullickson 6-1 6-1, then in the second round she double-bageled Kai-Chen Chang in 47 minutes, and today she defeated Yung-Jan Chan 6-1 6-0.

Wozniacki’s opponent in the fourth round will be former champion Maria Sharapova who didn’t let American hope Beatrice Capra win a single game and advanced with a 6-0 6-0 victory. However, the match lasted more than an hour, 73 minutes. (photo: © Neal Trousdale)

Fourth seed Jelena Jankovic was lucky to scrape through her first two rounds of the 2010 US Open, winning 6-4 4-6 7-5 against Simona Halep and 6-4 3-6 6-2 against Mirjana Lucic, but fell in straight sets in the third round to seed No.31 Kaia Kanepi, despite having a very good opportunity to take the match to the decider.

Jankovic lost the first set to Kanepi 6-2 in 32 minutes and found herself one game from defeat when the Estonian was serving at 5-3 in the second set. However, Jankovic won three games in a row and was serving to win the second set. Still, the comeback proved to be brief and Kanepi broke Jankovic to force a tiebreaker in which she quickly earned a 6-1 lead before converting her first match point. Final score: 6-2 7-6(1).

By reaching the fourth round of the US Open, Kanepi has recorded her best result at the tournament. Her next opponent will be either Patty Schnyder or seed No.15 Yanina Wickmayer. (photo: © Neal Trousdale)