Tennis: Azarenka knocks out Stephens

Victoria Azarenka of Belarus celebrates after beating Sloane Stephens of the U.S. during their first round match at the Australian Open tennis championship. Photo / AP

Two-time champion Victoria Azarenka has won her Australian Open first-round grudge match against Sloane Stephens, beating the American in straight sets at Melbourne Park for a third straight year.

Both players were unseeded for the first major of the year - with Azarenka having battled foot and knee injuries and personal issues in 2014, while Stephens suffered a slump in form.

But it was Azarenka who dominated Tuesday's encounter, winning 6-3 6-2 in 75 minutes to set up a big second-round clash with another former world No.1 - Denmark's Caroline Wozniacki.

In Stephens' first match against Azarenka two years ago, she accused the Belarusian of gamesmanship for taking a long medical timeout midway through their semi-final.

Last year, Stephens hit a forehand into Azarenka's groin region during their fourth-round match, with the American's attempts to apologise being ignored by the 2012 and 2013 Australian Open champion.

There were no further flashpoints on Tuesday, with Azarenka - who shapes as the most dangerous spoiler in the draw - advancing to a second-round clash with No.8 seed Caroline Wozniacki.

The Danish star was made to work hard in the first set by American Taylor Townsend before lifting in the second to win 7-6 (7-1) 6-2.

"You're always a little bit nervous - it's the first grand slam of the year," said Wozniacki.

"You like to start off well."

Last year's Open runner-up Dominika Cibulkova overcame a first-set blip to beat Belgian Kirsten Flipkens 3-6 6-3 6-1.

The Slovakian is seeded 11th, having enjoyed her best year on the tour in 2014.

Australian flagbearer Samantha Stosur, the No.20 seed, crushed Romania's Monica Niculescu 6-4 6-1.

No.24 seed Garbine Muguruza from Spain beat New Zealand's Marina Erakovic 7-5 6-0.

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-AAP