BRISBANE, Australia (AP) -- Serena Williams did a quick little dance behind the baseline to remind herself to move her feet. After a complete whiff at the net in the second set, she smiled ruefully and drew in some long, deep breaths.
She netted a service return on her first match point.
Top-ranked Williams' first competitive match of the season, on New Year's Eve, was by no means perfect, but the 6-4, 6-4 win over Andrea Petkovic at the Brisbane International was a decent start against a player who has been ranked as high as No. 9.
Williams made 36 unforced errors, including the big miss on Petkovic's floater in the fifth game of the second set, but hit 35 winners and fired 11 aces including one at 122 mph to bring up set point in the first.
''It was an intense match, which was really good,'' Williams said. ''She's been in the top 10 before and she was on her way to being even better. It was a good match for me.''
Petkovic is on her way back up the rankings after missing most of 2012 with injuries and started this season at No. 39.
Williams started 2013 in Brisbane with a title, the first of 11 for a year that included two major championships. She's back with the aim of carrying the momentum into 2014. She's already into the quarterfinals where she'll meet ninth-seeded Dominika Cibulkova, who overcame 43-year-old Japanese veteran Kimiko Date-Krumm 6-3, 1-6, 6-3.
Williams had a 78-4 record last season, won the French Open and U.S. Open and spent all but seven weeks atop the rankings, and she hasn't lowered her expectations for the year ahead.
''I had a similar question in 2012. I had such a good year winning two slams and a (Olympic) gold and two doubles. It was a lot,'' she said. ''I just didn't think I could do better. Arguably I may have done better (in 2013), so I'm just going to be up for that challenge again.''
The other featured women's player in Brisbane, third-seeded Maria Sharapova, received a walkover into the quarterfinals when her Australian opponent, 17-year-old qualifier Ashleigh Barty, withdrew with a left thigh injury on Tuesday evening.
Sharapova and Barty were scheduled to play Wednesday.
Barty, who will also miss next week's Hobart International, went through three rounds of qualifying in Brisbane to book her place in the main draw. She beat Daniela Hantuchova in the first round of the main draw.
''It's a tough decision but a smart one that we have to make,'' Barty said. ''It's pretty much just I need give myself, my body, 10 to 12 days to recover and hopefully be right for the Australian Open.''
In another second-round match, fourth-seeded Jelena Jankovic beat Elina Svitolina of Ukraine 6-1, 6-3.
On the men's side, Lleyton Hewitt beat Australian qualifier Thanasi Kokkinakis 6-3, 7-5, sixth-seeded Feliciano Lopez of Spain had a 6-4, 6-4 win over Mikhail Kukushkin of Kazakhstan and No. 8 Jeremy Chardy beat fellow Frenchman Adrian Mannarino 7-6 (4) 7-5.
There was a big upset in the WTA's ASB Classic at Auckland, New Zealand, where top-seeded Roberta Vinci of Italy lost 3-6, 6-4, 6-2 to 259th-ranked Ana Konjuh of Croatia. Konjuh, who celebrated her 16th birthday last Friday, is the reigning Australian and U.S. Open girls singles champion.
Fourth-seeded Sorana Cirstea of Romania and former champion Yanina Wickmayer of Belgium both lost to qualifiers, while second-seeded Ana Ivanovic and No. 3 Kirsten Flipkens advanced.
Former No. 1-ranked Ivanovic overcame a sore shoulder and saved four set points on serve on her way to a 7-5, 7-6 (2) win over American Alison Riske.
The second-seeded Ivanovic required treatment during the second set and played the latter stages with her right shoulder strapped.
At 3-5 and 0-40 down in the second, she faced the prospect of a difficult third set but strung together a series of powerful serves to save the game, then broke Riske to force a tiebreak.
At the Hopman Cup in Perth, Flavia Pennetta and Andreas Seppi beat Samantha Stosur and Bernard Tomic 6-3, 6-4 in the mixed doubles to give Italy a 2-1 win over Australia in Group A.
Pennetta beat Stosur 6-4, 6-4 in the singles before Tomic leveled with a 4-6, 6-3, 6-2 win over Seppi. It was Australia's second loss in the tournament.