Ash Barty is now guaranteed to keep the World No.1 ranking heading into the grass-court season after Naomi Osaka announced her shock withdrawal from the French Open.
Before Monday's announcement, World No.2 Osaka had an outside chance of taking Barty's No.1 ranking at Roland Garros.
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Because she won the French Open in 2019 and skipped the event in 2020, Barty is defending 2000 rankings points in Paris in 2021.
She will inevitably lose points if she doesn't win the title again.
After losing in the third round in 2020, Osaka was only defending 130 rankings points this year and could have reclaimed the No.1 ranking if Barty suffered an early exit.
Before Osaka's withdrawal, Barty had to reach the semi-finals to ensure she held into the top spot.
However she is now guaranteed to retain it after the French Open and beyond.
The Australian star has held the No.1 ranking since first overtaking Osaka in June of 2019 following back-to-back titles at Roland Garros and Birmingham.
She has now been World No.1 for 79 weeks - which ranks ninth all-time - only behind tennis legends Steffi Graf (377 weeks), Martina Navratilova (332), Serena Williams (319), Chris Evert (260), Martina Hingis (209), Monica Seles (178), Justine Henin (1170) and Lindsay Davenport (98).
Former grand slam champions crash out of French Open
As well as Osaka's withdrawal, Barty's quest for a second grand slam title was helped by some dramatic results on the opening two days of the clay-court tournament.
A total of six former grand slam champions have bowed out after the first round, with Garbine Muguruza, Angelique Kerber, Svetlana Kuznetsova, Bianca Andreescu and Jelena Ostapenko all joining Osaka in exiting the tournament.
Muguruza, Andreescu and Ostapenko all crashed out on Monday following losses for Kerber and Kuznetsove on Sunday.
Barty's biggest threat still remains defending champion Iga Swiatek, who launched her title defence by thrashing her buddy Kaja Juvan 6-0 7-5 on her birthday.
Swiatek, who turned 20 on Monday, moved into the second round in her bid to become the first woman since Justine Henin in 2007 to win consecutive French Open titles.
"It's never easy to play against your best friend," Swiatek told reporters later.
"You just try to block this friendship for two hours, just focus on the game. I think I'm doing that pretty well. It's nice to have that skill."
Swiatek will need all her skills to contend with Barty, who won the French Open in 2019 but skipped the trip in 2020 due to COVID-19 travel restrictions and risks.
Barty plays her first round match against Bernarda Pera of the US no earlier than 9.15pm on Tuesday night (AEDT).
On Monday, Andreescu became the highest women's seed to fall so far, losing a three-hour marathon against Tamara Zidansek.
The sixth seed and 2019 US Open champion went down 6-7(1) 7-6(2) 9-7 to the Slovenian, while Muguruza, who beat Serena Williams to win the title in 2016, was outplayed 6-1 6-4 by Ukraine's Marta Kostyuk.
And Latvia's Jelena Ostapenko, who blasted her way to the French Open title in 2017, lost 6-4 4-6 6-3 to last year's runner-up Sofia Kenin.
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