Australian Open: Naomi Osaka ends local challenge with Ashleigh Barty beating

Japan's Naomi Osaka overpowered Ashleigh Barty 6-4 6-2 to reach the fourth round of a grand slam for the first time on Saturday, leaving the host nation without a contender for the Australian Open women's title.

Barty's quantum leap from the outside the top 200 to number 17 in the world rankings over the last year had given some in Australia hope that the former cricketer might be a contender to end their 40-year wait for a women's champion.

Osaka shredded those hopes in 73 minutes on Rod Laver Arena, breaking Barty to open both sets and combining 12 aces, the last on match point, with 24 winners in a ruthless display of power tennis.

The 20-year-old Japanese, who is ranked 72nd and beat defending champion Angelique Kerber at the US Open last year, will next face Romania's world number one Simona Halep for a place in the quarter-finals.

Earlier on Saturday, a courageous Halep overcame three match points and throbbing ankle pain to edge out Lauren Davis 4-6 6-4 15-13 in a thrilling third round marathon.

The world number one fought back from the brink at 11-10 in the epic deciding set before finally serving out the contest on her fourth attempt after a taxing three hours and 44 minutes at Rod Laver Arena. She sealed the win on her first match point when 76th-ranked Davis fired a forehand into the tramlines, as the hard-hitting American coughed up a mind-boggling 73rd unforced error.

A shattered Halep declared herself "almost dead" in the wake of a 142-minute deciding set featuring more twists than the Transfagarasan mountain highway in her native Romania. It was a win, said the French Open finalist, that might have slipped through her fingers in years past.