Maria Sharapova of Russia hits a forehand return during a training session at the Brisbane International tennis tournament in Brisbane on December 30, 2012.   AFP PHOTO/William WEST  IMAGE RESTRICTED TO EDITORIAL USE - STRICTLY NO COMMERCIAL USE

Maria Sharapova during a training session at the Brisbane International. Photo: AFP

WORLD No.2 Maria Sharapova has withdrawn from the Brisbane International with a collarbone injury but says her Australian Open campaign remains on track.

Sharapova was due to play her first-round match in Brisbane on Wednesday but called a media conference on Tuesday afternoon where she confirmed she would take no part in the event.

The second seed is able to play groundstrokes but has only just resumed overhead shots as she tries to recover from the ailment, which also led to her withdrawal from an exhibition match in South Korea last week.

That injury was reported as a neck complaint but Sharapova confirmed it was the same problem that forced her to call time on the Brisbane tournament. She will head to Melbourne early and won’t play any other tournaments in the prelude to the opening  major event of the year.

The seeds continued to tumble in Brisbane. The tournament featured eight of the world’s top 10 female players but after Sharapova’s withdrawal, only three remain, with Sara Errani and Petra Kvitova joining Sam Stosur and Caroline  Wosniacki on the losers’ list.

Italy’s fifth seed Errani was beaten 4-6, 6-1, 7-5 by Daniela Hantuchova, and Czech sixth seed Kvitova fell 6-4, 7-5  to Russian Anastasia Pavlyuchenkova.

But tournament favourite Serena Williams demolished Frenchwoman Alize Cornet 6-2, 6-2 to canter into the quarter-finals.

Williams touched 200 km/h with some of her serves as she completed a regulation shift, moving on to face either countrywoman Sloane Stephens or Swede Sofia Arvidsson, the surprise winner over Stosur.

In the men’s draw, Queensland qualifier John Millman defeated Japan’s Tatsuma Ito 6-4, 6-1 to set up a meeting with world No.3 Andy Murray.

Given the pedigree of the man he now faces, common sense dictates that’s about as far as Millman is going to get.

But he remains determined not to pack a white flag in his kit bag in his home-town tournament.

“I’ve never played him, never hit with him. There’s no point in hiding the fact he’s one of the world’s best players,” Millman said.

“I definitely can’t go in there being beaten before I go out and even play. I feel as if I deserve to be playing on centre court against Andy Murray. I’ve qualified, I’ve beaten Tatsuma Ito today and I’ve been playing really well.’’

Countryman Matthew Ebden failed to advance on Tuesday.   He was tipped out in the first round by Belgian David Goffin 6-2, 6-2.