Naomi Osaka dents Ash Barty's quest to end season as World No.1

Ash Barty lost to Naomi Osaka in the 2019 China Open final. (Getty Images)

Naomi Osaka has put Ashleigh Barty's quest for the year end No.1 on hold for now after the Japanese's three-set win in the China Open final.

Osaka fought back to register a 3-6 6-3 6-2 win in one hour and 50 minutes in Beijing.

‘CAN’T BELIEVE IT’: Ash Barty at centre of 'incredible' drama at China Open

Barty is still in a strong position to become the first Australian woman in the professional era to end the year on top of the rankings however as she remains more than 1000 points clear of world No.2 Karolina Pliskova.

Earlier in the day, Aussie John Millman finished short of claiming his first ATP title after losing the final of the Japan Open in straight sets to Novak Djokovic.

Naomi Osaka of Japan (R) shakes hands with Ashleigh Barty of Australia after Osaka won their women's singles final at the China Open tennis tournament in Beijing on October 6, 2019. (Photo by GREG BAKER/AFP via Getty Images)

The Australian was no match for the world No.1, going down 6-3 6-2.

Still, it was an excellent week for Millman who is expected to get a rankings boost from No.80 to No.58 in the world as well as a pay day of $A289,000.

The 30 year-old enjoyed a remarkable run through to what was just his second ATP final, winning a total of six matches including two in qualifying.

He had survived three match points in his opening-round qualifier against American Bradley Klahn, but powered through the draw which opened up nicely for him as seeded players such as Borna Coric and Benoit Paire fell by the wayside.

[Join or create a 2019 Yahoo Fantasy Basketball league for free today]

Millman started confidently and pushed Djokovic in the opening service game on Sunday but was effectively playing catch-up for most of the set.

Djokovic required just one break in the fourth game to eventually take it 6-3.

Things started inauspiciously for the Queenslander in the second, getting broken after holding a 40-15 advantage.

From there, it was all the Serb as he charged through the set to claim his first title in Tokyo, fourth of the year and 76th of his career.