Ashleigh Barty has vowed to maintain focus at the season-ending WTA Finals after securing the year-end No.1 ranking on Sunday.

The French Open champion’s 5-7, 6-1, 6-2 victory over Belinda Bencic saw her become Australia’s first year-end No.1 since Lleyton Hewitt in 2002.

Barty, who started the year ranked 15, has had a meteoric rise and won a tour-topping 53 matches this season.

“It’s been an incredible year,” Barty told reporters. “I think it’s a bit of a bonus to be able to finish year-end world No. 1. It certainly wasn’t something that was in my realm at the start of the year.”

The 23-year-old said her eye was still on the main prize at the $14 million round-robin tournament.

“I think first and foremost, we’d love to finish off the week here really strongly, then we can worry about celebrating that little thing [No.1 ranking],” Barty said.

“I think it’s a bonus now knowing I’ve started well. But it doesn’t change my preparation for Tuesday’s match in any regard,” she added.

Barty’s next match will be a Red Group blockbuster against world No.3 Naomi Osaka, who defeated Petra Kvitova 7-6 (7/1), 4-6, 6-4 in a marathon encounter to thrillingly open the WTA Finals.

It is a chance for Barty to exact revenge on the Japanese sensation who won a three-set final in Beijing earlier this month.

In-form Osaka has won 11 straight matches after titles in Beijing and Osaka.

“It’s refreshing knowing that I get to play her now having just played her a few weeks ago in Beijing,” Barty said.

“I learnt a lot from the match in Beijing. I’ll try to take as much as I can into the match come Tuesday.”

Barty’s season is set to extend past the WTA Finals as she spearheads Australia’s Fed Cup title hopes against France in next month’s final.