Australian Open: Defending champion Victoria Azarenka in quarters

Victoria Azarenka blasted past young American Sloane Stephens and into the Australian Open quarter-finals on Monday as the defending champion hit top form.

The Belarusian second seed blitzed into a last-eight clash with either fifth seed Agnieska Radwanska or exciting young Spaniard Garbine Muguruza with a 6-3, 6-2 win in 91 minutes.

With Serena Williams and Maria Sharapova both fourth-round casualties, Azarenka is well-placed to become the first woman to win the title in three consecutive years since Martina Hingis between 1997-99.

The 24-year-old is yet to drop a set and appears to be peaking at the right time as she stretched her win streak at Melbourne Park to 18 matches.

"It was a tough match but I was ready to battle for as long as it took," she said.

"I'm glad I could find my rhythm and go for my shots. I just love playing here. It feels so cosy, it feels like home," she added of Rod Laver Arena.

It was her first meeting with 20-year-old Stephens, the 13th seed, since their controversial last-four clash here in 2013.

During that match, Azarenka walked off court for a medical timeout after Stephens had saved five match points and broken the Belarusian.

She returned after a slow hand clap from the crowd and Stephens won only three more points, losing 6-1, 6-4 and leading to accusations of gamesmanship from some quarters.

Azarenka later said she had been troubled by a rib injury.

Before Monday's match the pair insisted any hostilities were in the past, although Stephens admitted their relationship was "non-existent, suggesting an undercurrent of ill-feeling.

Azarenka, nicknamed "Vika", comfortably held serve to get the match underway in warm conditions, as did Stephens, who has had a consistent Grand Slam record over the past year, reaching at least the fourth round on each occasion but is yet to win her first career title.

Despite Azarenka firing two double-faults in her second service game, Stephens was unable to capitalise and she paid the price when her serve was broken in the fourth game on a wayward backhand.

The defending champion's probing returns and pinpoint baseline shots were troubling Stephens, who had to dig deep to save six break points in the sixth game.

But she was unable to get the break back as Azarenka kept the pressure on to take the set.

Stephens was being forced into too many errors and her confidence was being sapped by the relentless and determined second seed, who scored another crucial break in the first game of the second set.

Azarenka refused to give an inch, running down every shot as they both held serve. But Stephens was not giving up, holding firm in an eight-minute game to stay in touch at 2-3.

But Azarenka was in a different class and she forced another break with a looping forehand winner before serving out for the match to continue her march towards another title.