For the first time since the tour resumed play last July, the No.1 ranking could change hands at the Miami Open, where World No.1 Ashleigh Barty and No.2 Naomi Osaka are in action.

This week, the WTA announced adjustments to the WTA ranking system to account for the continued schedule modifications affecting the tour calendar following the 2020 pandemic-shortened season. 

Under the adjusted WTA Ranking system and rules set forth, the following tournaments will be dropped from a player’s ranking summary on Monday, April 5: 2019 Miami, 2019 Guadalajara, 2019 Charleston and 2019 Monterrey. 

Points earned at this year’s Miami Open will be added. However, Miami will not be considered a mandatory result that must be counted as part of a player's best 16 results. 

In regard to the WTA World No.1 ranking in singles, Osaka will have the opportunity to overtake current No.1 Barty after Miami.

Osaka would need to reach the Miami final. However, if Barty advances to the semifinals, then Osaka would need to win the title.

Update: Barty has advanced to the semifinals after defeating Aryna Sabalenka in Tuesday's quarterfinal. Osaka must now win the Miami title for a chance to return to No.1.

If Barty returns to the Miami final, she will extend her stay at No.1, regardless of Osaka's results.

Since Osaka made history to become the first Japanese No.1 after winning the 2019 Australian Open, only she or Barty have held the top spot. 

Barty first overtook Osaka to become No.1 for the first time on June 24, 2019, after winning back-to-back titles at Roland Garros and the Nature Valley Classic. The 24-year-old Queenslander is the first Australian woman to hold the top spot since Evonne Goolagong Cawley. 

Osaka retook the No.1 ranking briefly in August of 2019 before Barty reclaimed the mantle on Sept. 9, 2019. Barty has held on for 62 consecutive weeks (including the weeks of Miami) and 69 weeks overall. Osaka has held the top spot for 25 non-consecutive weeks.

The World No.2 has advanced to the quarterfinals in Miami for the first time in her career after defeating Elise Mertens 6-3, 6-3. Osaka kicked off her Miami Open campaign with a 7-6(3), 6-4 win over Ajla Tomljanovic. Osaka has now won 23 consecutive matches and has not lost since February 2020. The reigning Australian Open champion faces Maria Sakkari on Wednesday.

How Barty saved MP and avoided an early exit in Miami

Barty has had a far more adventurous start to her title defense. The defending champion is battling jet lag after a 50-hour travel day from Australia to Florida and had to save a match point to defeat Kristina Kucova 6-3, 4-6, 7-5 in her opener, but bounced back with a solid 6-3, 6-2 win over Jelena Ostapenko. 

Barty advanced to the quarterfinals with a 6-1, 1-6, 6-2 win over Victoria Azarenka in the fourth round. She is back in the semifinals after defeating Sabalenka 6-4, 6-7, 6-3 on Tuesday. 

This post has been updated to reflect Barty and Osaka's progression through the tournament