Osaka hasn't lost a single match since the resumption of the tour last August. The 23-year-old won the US Open in September and the Australian Open in February, amid an ongoing 21-match unbeaten streak.
Ashleigh Barty, meanwhlie, did not play any event last year after the tour resumed. And this year, the 24-year-old has posted a 9-2 record while playing three events in Australia.
Despite the sharp contrast in their recent results, Naomi Osaka has remained at No. 2 in the rankings behind Ashleigh Barty. That is mainly due to the pandemic-induced adjusted ranking system adopted by the WTA tour last year.
But that system was initially declared to be effective only until March 2021. Barring any further changes (which are yet to be announced), it is understood that WTA players will start losing their 2019 ranking points from this month.
Ashleigh Barty achieved the top ranking for the first time in June 2019. After losing it for a few weeks in August of that year, the Aussie regained the numero uno spot in September 2019 and has remained there ever since.
Naomi Osaka has also been ranked World No. 1 in the past. In fact, Osaka was the one who displaced Barty briefly in August 2019.
Now, with both players taking part in the Miami Open, the No. 1 spot is up for grabs.
Having won the 2019 Miami Open, Ashleigh Barty is defending 1,000 points of her current tally of 9,186 this fortnight. On the other hand, Naomi Osaka reached the third round of the 2019 Miami Open, which earned her only 65 points.
A title for Osaka this fortnight would increase her ranking points tally by 935 points, taking her total from 7,835 to 8,770. If the Japanese does win the title, Barty will need to reach at least the final in Miami to retain the No. 1 ranking.
A few other scenarios could also enable Naomi Osaka to take the top spot from Ashleigh Barty, but those are unlikely since they are based on a combination of results.
Naomi Osaka and Ashleigh Barty are the top two seeds for the Miami Open
The main draw at the Miami Open starts on Wednesday. Top seed Ashleigh Barty has a bye in the first round, and will face a qualifier in the second.
No. 2 seeded Naomi Osaka, meanwhile, will face Ajla Tomljanovic or Anastasia Potapova in the second round.
19 of the world's top 20 women, with the notable exception of 23-time Major champmion Serena Williams, are entered in Miami. Williams pulled out over the weekend due to her recent oral surgery.
The Miami Open is being played with limited crowds this year, and a steep cut in prize money. While the 2019 edition had a prize pool of $16.7 million for the combined men's and women's event, the 2021 edition's total prize money stands at $6.68 million.