Wozniacki in bid for US title double

Caroline Wozniacki of Denmark hits a backhand return against Bethanie Mattek-Sands during the Sony Ericsson Open at Crandon Park Tennis Center on March 24, 2011 in Key Biscayne, Florida. AFP

Wozniacki reached the third round of the $9 million event with a 6-2, 7-5 victory over American Bethanie Mattek-Sands.

"Especially in the first match you want to get going, you want to have the rallies," said the Dane, who like all the top seeds enjoyed a first-round bye.

"But I really couldn't get that today, so I just had to fight. I thought I did that pretty well."

Wozniacki, who took the top ranking from Australian Open champion Kim Clijsters and backed up her move by winning the prestige trophy in the California desert on Sunday, remains the woman to beat this week.

The 20-year-old said she feels energized, despite her long run at Indian Wells.

"I'm actually feeling pretty good, I'm not really tired. Hopefully I'll play long in this tournament. I'll have a day in between matches, I'm just enjoying myself out there."

Roland Garros finalist Samantha Stosur of Australia, seeded fourth, beat China's Zheng Jie 6-2, 6-1.

Stosur has been getting off to fast starts, having won her opening match at her previous seven events.

"I thought I played quite well," said Stosur. "I don't think I hit the ball out of this world fantastic, but I guess I did what I had to do."

The loss was the fifth for Zheng this season, with the Chinese player managing only two wins.

Serbian sixth seed Jelena Jankovic took an easy victory over Romanian Monica Niculescu 6-3, 6-1 while 11th seed Svetlana Kuznetsova bounced back after a first-round defeat at Indian Wells to dispatch Simona Halep 6-0, 6-4.

Maria Sharapova, seeded 16th and making her first Miami appearance since 2007 after battling a string of injuries, launched her campaign with a 6-3, 6-2 victory over Croatian Petra Martic.

Men's seeds were resting and training before starting on Friday, with supporting acts taking center stage.

Japan's top ATP player, Kei Nishikori, offered some modest cheer to his stricken homeland with his defeat of Frenchman Jeremy Chardy 7-6 (7-5), 6-2 in the first round.

Nishikori was among some 15 ATP stars who took part in a benefit football match on Wednesday night, raising money for the American Red Cross' Japan relief efforts.

He said he was touched by the concern his colleagues had shown for his homeland.

"I want to thank all the players for helping Japan like that. I'm very proud -- and I had fun yesterday," he said.

Australian Open champion Novak Djokovic was the prime mover behind the charity football match, won by the Fort Lauderdale Strikers 4-2, and said Thursday it had been a rousing success.

He said the ATP players were already devising similar events to help those in need in the wake of the March 11 earthquake and tsunami in Japan.

"This gives us ideas over the next couple of months to organize another game somewhere in Europe, maybe with some big team," said Djokovic, the hottest racquet on the ATP with an 18-0 record and three titles in 2011.

"I'm not going to say where and when," he added, "but we have something in our minds."

Djokovic has yet to open his Miami campaign. Other men in action Thursday included his Serbian compatriot Janko Tipsarevic, who beat Robin Haase of the Netherlands 6-4, 7-6 (7/5) while Spaniards Feliciano Lopez and Ramon Ramirez Hidalgo both reached the second round.