Rusty Serena marches on at Brisbane International

World No 1 Serena Williams showed plenty of rust in her first competitive outing of the year ahead of the Australian Open, but battled through to defeat Andrea Petkovic in straight sets at the Brisbane International on Tuesday.

The number one seed won 6-4, 6-4 in 98 minutes to reach the quarter-finals but her 36 unforced errors and 55 percent serving accuracy shows how much Williams has to work on with the first major of 2014 less than a fortnight away.

German opponent Petkovic was exactly what the defending champion needed at this point in the season. Ranked 43rd in the world, but a top-ten player before multiple injuries restricted her 2012 campaign, she ensured the five-time Australian Open winner had to fight for every point.

"It was an intense match, which was really good for me," Williams told reporters. "She's a good player. She's been in the top ten before and she was on her way to being even better."

In their only previous match Petkovic took the American to three sets, on clay in Rome in 2010, and looked capable of doing so once more after nullifying an early break and taking a 4-3 lead in the first set.

Williams then held her serve to love and an easy missed volley into the net gifted the 17-time grand slam winner a break in the next, leading to Petkovic slamming her racquet into thigh, floor and bag in turn.

In her first tournament match since the 2013 WTA Championships in October, Williams showed frustration throughout at the extent of her erratic play.

There were serves fired in at over 190 kilometres and 35 crunching winners, but even more mistakes.

After errant serves she would often practice her ball toss or technique, reinforcing the sessions spent with her father, Richard, in Florida during the off-season.

"I'm a renowned perfectionist --I think I wrote the book on being perfect," Williams said.

"I think it definitely helps me in a way.

"Also, it definitely holds me back at some moments. It's just important for me to let the part that helps me kind of fill up and then the part that holds me back, just to let that go."

Her most glaring error came in the sixth game of the second set when a looping backhand from Petkovic landed just over the net to set up an easy winner but Williams was fooled by prodigious backspin and wildly missed the ball with a forehand.

The crowd at Pat Rafter Arena roared with laughter and even Williams smiled, briefly.

Petkovic, who qualified for the second round by beating Williams' compatriot Bethanie Mattek-Sands in straight sets, surrendered a 40-0 lead on serve in the fifth game of the second set, which the world number one ended up taking.

The German saved the first match point on her serve, but a forehand into the net in the following game gave Williams victory.

Williams next plays ninth-seed Slovakian Daniele Cibulkova who defeated Japanese veteran Kimiko Date-Krumm 6-3, 1-6, 6-3.

On the other side of the draw in Brisbane, fourth-seed Jelena Jankovic beat Ukrainian Elina Svitolina 6-1, 6-3, keeping the Serb on course for a semi-final meeting with defendings Australian Open champion Victoria Azarenka.

Image: Serena Williams of the USA reacts after winning a point against Andrea Petkovic of Germany at the Brisbane International at Queensland Tennis Centre on Tuesday

Photograph: Bradley Kanaris/Getty Images