MELBOURNE, Australia (AP)—Venus Williams let out a scream and doubled over in agony after hitting a shot in her first-set tiebreaker at the Australian Open.

Williams had strained a hip muscle and later said she was in so much pain that if she hadn’t been playing in a Grand Slam, she likely would have retired from the match.

Instead, she took a medical timeout, had her upper right thigh wrapped and rallied for a 6-7 (6), 6-0, 6-4 second-round win Wednesday over Czech opponent Sandra Zahlavova. That kept intact her streak of 257 straight singles matches at majors without a retirement.

“This being a major definitely has a lot to do with me staying on the court,” Williams said. “Obviously, I wasn’t able to play at my exact level, so I had to play smarter and hang tough.”

Her mother, Oracene Price, had yelled encouragement to “fight” during the tiebreaker at Rod Laver Arena.

Williams, the winner of seven Grand Slam singles titles, managed to track down most of the angled shots from Zahlavova in the second set despite the injury. The 97th-ranked Zahlavova didn’t win a game in the set.

Williams was able to hit winners from the baseline, relying on her powerful groundstrokes to keep rallies short. The fifth-ranked Williams broke Zahlavova’s serve in the seventh game of the third set and served out the match.

The 30-year-old Williams isn’t sure how the injury will respond to treatment before her next match against 33rd-ranked Andrea Petkovic of Germany.

“I’m going to try to recover for Friday and get ready to play and bring my best tennis,” she said. “Hopefully, I can come through.”

She needed assistance after the match, asking courtside staff and officials to help carry her equipment, bag and rackets.

Williams carried her handbag, which went with her outfit—a lattice-style top with a multicolored satin short skirt she later referred to as her “Alice in Wonderland” outfit.

“It was really tough, but I’m a long way from home and it’s such a long way I didn’t want to go back yet,” Williams said. “You’ve got to be able to play under all kinds of circumstances—good, bad, strange, weird, all of the above.

“When I look back, I have no regrets that I could have done more or I could have done less. For me, it’s peace of mind. I think what keeps me going is knowing that when I’m healthy, I play really, really well.”

There was no such drama when Caroline Wozniacki advanced with an emphatic 6-1, 6-0 win over American Vania King as her first major atop the rankings continued to gather momentum.

The 20-year-old Danish player was never troubled in the 58-minute match, breaking 88th-ranked King’s serve to finish it off and reach the third round for a 13th consecutive Grand Slam tournament. She has yet to win a major, but has held the No. 1 ranking since October and can retain it by reaching the semifinals here.

To get to the semis, she might have to beat seven-time Grand Slam winner Justine Henin, who continued her comeback from injury with a 6-1, 6-3 win over Elena Baltacha of Britain on center court.

The pair could meet in the quarterfinals. Henin will have to get through a tough match against two-time major winner Svetlana Kuznetsova just to get past the third round. The 23-seeded Kuznetsova beat Dutch qualifier Arantxa Rus 6-1, 6-4.

“I have a lot of good memories, almost all good memories, from Melbourne,” said Henin, the 2004 Australian champion and runner-up here in 2006 and last year, when she was returning from a career break from the tour.

Her comeback was stalled after Wimbledon—she couldn’t play because of an elbow injury—and is making another return of sorts at Melbourne Park.

Henin is one of two former Australian Open champions in the women’s draw. The other, 14th-seeded Maria Sharapova, was only a point from slipping behind 4-0 in the first set before she recovered to beat Virginie Razzano 7-6 (3), 6-3. Sharapova, who won the 2008 Australian title, missed the 2009 tournament due to injury and was ousted in a first-round upset last year.

No. 8 Victoria Azarenka, the 2010 quarterfinalist who has lost to Serena Williams the past three years here, beat Andrea Hlavackova 6-4, 6-4. Serena Williams is injured and not defending her title in Australia.

On the men’s side, Wimbledon finalist Tomas Berdych needed four match points, struggling to finish it off with his serve in the last game, to beat Philipp Kohlschreiber 4-6, 6-2, 6-3, 6-4.

No. 8 Andy Roddick had no such trouble, firing his 17th ace to finish off a 7-6 (7), 6-2, 6-3 second-round win over Igor Kunitsyn of Russia.

The former No. 1-ranked Roddick is into the third round at Melbourne Park for the ninth straight time.

He said he was finding his range.

“I think when you’re confident, the court just makes sense; decisions come easier to you,” he said. “A lot of it comes naturally. There’s not a whole lot of thought process. You’re not forcing a lot. The ball kind of, I guess, reacts the way you want it to.

“So I feel comfortable out there right now.”

Roddick’s friend and U.S. Davis Cup teammate Mardy Fish made a second-round exit, the No. 16 seed losing 1-6, 6-3, 6-3, 6-3 to Tommy Robredo.

No. 9 Fernando Verdasco rallied from two sets down to beat Serbia’s Janko Tipsarevic 2-6, 4-6, 6-4, 7-6 (0), 6-0, conceding just one point on his serve in the last set. Verdasco has a history of five-set matches here—his 5-hour, 14-minute semifinal loss to Rafael Nadal two years ago was the longest match ever at the Australian Open.

No. 17 Ivan Ljubicic and No. 28 Richard Gasquet also advanced, while Japan’s Kei Nishikori beat Germany’s Florian Mayer 6-4, 6-3, 0-6, 6-3. Other seeded men eliminated were No. 25 Albert Montanes and No. 26 Juan Monaco.