Sydney, Aug 8 (IANS): Young tennis star Ash Barty lost her world number one ranking on Thursday, handing back the top spot to Japan's Naomi Osaka.

While the 23-year-old Aussie has been a consistent performer over the past year, culminating in her maiden Grand Slam title at the French Open back in June, a fourth round exit at Wimbledon and a shock second round loss to American Sofia Kenin 6-7 (5-7), 6-3, 6-4 at the Canadian Open in Toronto on Tuesday meant the door was open for Osaka to regain her number one status, reports Xinhua news agency.

Taking on Tatjana Maria in Toronto on Thursday, Osaka won the first set of the tournament's round of 32-match 6-2, before her German opponent retired from the contest with an injury.

But the two-time Grand Slam Champion's position at the top of the rankings could be short-lived with Czech hitter Karolina Pliskova breathing down the necks of both Osaka and Barty.

A strong run in the tournament could see the 27-year-old leap-frog the pair of Osaka and Barty and pick up the number one ranking for the second time in her career.