Top seeds Novak Djokovic of Serbia and Caroline Wozniacki of Denmark were among 32 top seeds in each draw who received first-round byes.

Zheng outlasted Romania's Sorana Cirstea 6-3, 6-7 (5/7), 6-3 to book a second-round matchup with Australian fourth seed Samantha Stosur.

Baltacha rallied to defeat Austria's Sybille Bammer 3-6, 7-6 (7/5), 7-6 (7/5). The 27-year-old daughter of a former Soviet Union international footballer - ranked 55 in the world - will next face 32nd-seeded Klara Zakopalova of the Czech Republic.

Croatian wild card Petra Martic booked a second-round matchup with Russian 16th seed Maria Sharapova by defeating Germany's Kristina Barrois 7-5, 6-2.

Romanian Monica Niculescu defeated Serbia's Bojana Jovanovski 6-1, 7-6 (7/2) to reach a second-round date with Serbian sixth seed Jelena Jankovic.

American Melanie Oudin ousted Germany's Julia Goerges 7-5, 6-3 and will face Slovakian 29th seed Daniela Hantuchova next with a third-round matchup possible against top seed Wozniacki.
 

Caroline Wozniacki is No. 1 without winning a Grand Slam tournament — and she has no problem with that.

“I’ve won quite a few tournaments the last year and I feel like I’m playing great tennis at the moment,” she said during a news conference for the Sony Ericsson Open. “I feel I deserve to be where I am.

“I’m 20 and No. 1. A lot of people want to be in my footsteps.”

Wozniacki’s already won two titles this year: Dubai and Indian Wells. She did, however, fall short at the Australian Open, losing in the semifinals to Li Na of China.

In 2010, Wozniacki won six of her 14 career titles. But her best 2010 Grand Slam result was a US Open semifinal appearance.

Wozniacki’s only career Grand Slam final was at the 2009 US Open, where she lost in straight sets to Kim Clijsters.

Clijsters, the Sony Ericsson Open defending champion, also makes a good case for being No. 1 in the world as the reigning champion of the last two majors: the 2010 US Open and 2011 Australian Open.

Clijsters did push Wozniacki out of the No. 1 ranking for the week of Feb. 14, 2011. But Wozniacki returned to top billing the following week and will remain at No. 1 at least through April 10, 2011.

“Kim deserves to be No. 1 as well,” said No. 5 Sam Stosur of Australia. “I can’t really say anything except, unfortunately, that’s the way the rankings work for the players who don’t play as much.”

Stosur, however, acknowledges Wozniacki’s play the past year has been impressive.

“If she’s No. 1 without winning one (a Grand Slam) then that’s credit to her for doing well every single week and being ultra consistent,” Stosur said.

Clijsters said a shoulder injury that forced her to retire from a fourth-round match against Marion Bartoli of France at Indian Wells is much better. She anticipates no problem attempting to defend her title this week.

For her part, Clijsters wasn’t all that interested in debating the No. 1 issue. She’s been top-ranked for 20 weeks throughout her career.

“To me, it’s not something I’m focused on and aiming for,” Clijsters said. “I’m happy she enjoys the whole role because when you’re number one there’s even more things to do.

“Let somebody else do that.”