Ashleigh Barty has capped her watershed season with the Australian No.1 ranking.
Daria Gavrilova's second-round exit from the Kremlin Cup, where she was runner-up last year, has ensured Barty will leapfrog her in the rankings on Monday and climb to a career-high 21st in the world.
Gavrilova will fall two spots to 24th and faces an anxious wait before learning if she's qualified for the season-ending WTA Elite Trophy being staged in Zhuhai from October 31.
The 23-year-old was trailing Belarusian qualifier Vera Lapko 6-3 3-1 when she quit with a right leg injury.
Fatigue also likely played a part in her mid-match retirement after Gavrilova lost a sapping three-hour three-set final to Russian Anastasia Pavlyuchenkova in Hong Kong on Sunday night, before making a mad dash to Europe for her opening match in Moscow less than 24 hours later.
"My body is very confused what time zone it's in ?!?!?!?!?!?," Gavrilova tweeted after Wednesday's defeat.
Gavrilova is 22nd in the WTA points race, with those ranked ninth to 19th invited to join Chinese wildcard Peng Shai in Zhuhai.
But the Russian-born star still may get the chance to jostle with Barty for the year-end Australian No.1 ranking, which she has held since Samantha Stosur relinquished in June after a record 442 consecutive weeks.
World No.9 Johanna Konta has called an end to her season, while US Open runner-up Madison Keys is in doubt after being sidelined with injury.
In the meantime, Barty can enjoy her time in the sun ahead of her appearance in the doubles at next week's WTA Tour Finals in Singapore with fellow Australian Casey Dellacqua.
Incredibly, Barty began 2017 ranked 271st in the world after her return to the tour last season following a 20-month sabbatical and stint playing cricket in the Women's BBL with Brisbane Heat.
The 21-year-old's breakout season has included a maiden WTA singles title in Kuala Lumpar and further finals in Birmingham and Wuhan.