Top women players suffer shock exits at WTA Miami

Seventh seed Ana Ivanovic of Serbia and Russian sixth seed Vera Zvonareva also endured surprise elimination, but it was business as usual for the top ranked men with Roger Federer, Andy Roddick and Novak Djokovic all jaunting through.

Safina lost 6-1 6-4 to unseeded Australian Samantha Stosur and described the rain-interrupted encounter as a "disaster".

"It was just bad match for me. It was just a disaster match," said a stern-faced Safina.

"I started to play a little bit better at 6-1 3-0 but I had put the game in her hands and it was too late," the second seed added, blaming fatigue for her form. Stosur, ranked 42nd in the world, will face France's Amelie Mauresmo, an impressive three-sets victor over Italian Flavia Pennetta.

Hungarian Agnes Szavay, ranked 25th, beat Ivanovic 6-4 4-6 6-1 in another rain-affected match. Ivanovic's exit completed a bad weekend for Serbia after her compatriot Jelena Jankovic was knocked out in the second round by Argentine Gisela Dulko.

"I hardly did anything well today. I was trying to come in, and I was volleying pretty well at times, but I was really disappointed. I couldn't really hold my serve," Ivanovic said.

Zvonareva went out to Li Na of China 6-4 3-6 6-2.

While Serbs and Russians fell away, America's Williams sisters marched on.

Venus beat battling German Anna-Lena Groenefeld 7-5 6-3 while world number one Serena gave up a game fewer on her way to a 7-5 6-2 victory over China's Peng Shuai.

Serena will face another Chinese player, Wimbledon semi-finalist Zheng Jie, on Monday.

In the men's event, American Roddick survived a grueling first set tiebreak against Russian Dmitry Tursunov, which he won 11-9, before going on to ease through the second set 6-2.

World number two Federer enjoyed a routine 6-4 6-1 win over German Nicolas Kiefer but will face a surprise opponent in the fourth round after 15th-ranked Spaniard Tommy Robredo lost 7-5 6-3 to American qualifier Taylor Dent.

Dent's career looked finished in 2007 after he spent most of the year in a cast following a serious back injury.

Serbian number three seed Djokovic gave at least some satisfaction to his country with a comfortable 6-4 6-1 win over Frenchman Paul-Henri Mathieu.