Following Ashleigh Barty's retirement this week and her decision to remove herself from the Hologic WTA Tour rankings, the World No.1 position is unexpectedly in play at the Miami Open. It could be decided as soon as Day 4. Iga Swiatek will ascend to the summit either if she wins her opening match or if Paula Badosa loses. If Swiatek loses her opening match, Badosa will still need to win the tournament to reach No.1.
Viktorija Golubic (SUI) vs.  Iga Swiatek (POL)
Swiatek is riding high on an 11-match winning streak, the longest of her career at WTA level, after sweeping the first two WTA 1000 tournaments of the year in Doha and Indian Wells. Her commitment to more aggressive tactics and her confidence to deploy this on big points has been evident throughout her run, particularly in victories over Maria Sakkari, Angelique Kerber and Simona Halep.
Golubic, 29, is a tricky opener, though. The stylish Swiss and her rare one-handed backhand enjoyed a career-best season in 2021, breaking the Top 50 for the first time, and she has historically challenged Swiatek. Golubic won their first meeting at Wimbledon 2019, and was the only player to take a set from the Pole in Doha last month.
Deep runs at Indian Wells and Miami consecutively are also rare. In the past 15 years, the only Indian Wells champions to reach the Miami semifinals immediately afterward are Maria Sharapova (2013), Simona Halep (2015) and Victoria Azarenka (2016).
 Paula Badosa (ESP) vs. [Q] Marie Bouzkova (CZE)
Back in 2015, Badosa made her WTA main-draw debut in Miami as a No.419-ranked wildcard, reaching the third round. Seven years on, she could potentially leap from her current No.6 to No.1.
The 24-year-old Spaniard brings a 13-5 season record into the tournament, including an impressive semifinal run in Indian Wells that included victories over Leylah Fernandez and Sara Sorribes Tormo. She'll need to have similar patience against a resurgent Bouzkova. The Czech was on the verge of falling out of the Top 100 in February but has won 14 of her past 17 matches, including a third WTA final in Guadalajara. Bouzkova will be seeking her fifth career Top 10 win.
Head-to-head: Badosa leads 1-0, a 6-4, 6-3 win in the second round of the 2017 Las Vegas ITF W60 event.
Shelby Rogers (USA) vs.  Jelena Ostapenko (LAT)
Ostapenko surged back into the Top 20 after a stellar February, in which the Dubai title was bookended by semifinal runs in St. Petersburg and Doha. But the Latvian was tripped at the first hurdle in Indian Wells by perennial upset artist Rogers, who now owns 21 victories over Top 20 players even though she is yet to crack the Top 30 herself.
Two weeks on, Ostapenko has a chance for revenge at the same stage of Miami. The 2018 runner-up, she is one of only four players in the field who have reached the final here.
Head-to-head: Ostapenko leads 3-1. On hard courts, they are tied at 1-1.
 Coco Gauff (USA) vs. [Q] Wang Qiang (CHN)
Like Ostapenko, Gauff has an opportunity to avenge a surprise loss this year. The American was upset by Wang Qiang in the first round of the Australian Open, despite a previous 2-0 head-to-head lead and Wang's apparent poor form prior to the year's first major.
In retrospect, the defeat seems less of a problem. Wang, it transpired, was just getting her resurgence started; the former World No.12 has now won 12 of her past 16 matches, including a semifinal run in Guadalajara, to return to the brink of the Top 100. Gauff also bounced back to reach the Doha quarterfinals and third round of Indian Wells.
Wang had to battle hard to escape another 2004-born American in the first round, defeating wildcard Ashlyn Krueger 4-6, 7-5, 6-2. Both players are former Miami quarterfinalists, Wang having reached that stage in 2019 and Gauff in 2021.
Head-to-head: Gauff leads 2-1 overall; Wang leads 1-0 on hard courts.
Best of the rest
An all-American derby sees No.16 seed Jessica Pegula take on 2018 champion Sloane Stephens, one of only two former Miami titlists in the draw. Both players lost their Indian Wells openers, Pegula to Marie Bouzkova and Stephens to Naomi Osaka. Pegula was the victor in their only previous encounter, in the second round of Indian Wells 2021.
The other former winner in this year's field is three-time champion Victoria Azarenka, who lifted the trophy in 2009, 2011 and 2016. The No.12 seed will seek to maintain an unbeaten record against Ekaterina Alexandrova in their first hard-court encounter.
No.3 seed Maria Sakkari, fresh off her first WTA 1000 final in Indian Wells and at a career high, now owns a 16-5 record this year. The Greek will aim to keep her form going against Monterrey semifinalist Beatriz Haddad Maia, who has risen from No.342 to No.62 over the past 12 months. Haddad Maia won their only previous meeting 6-3, 6-1, in the 2014 Merida ITF W25 quarterfinals.
No.30 seed Marketa Vondrousova will take on Yulia Putintseva in a clash between two of the best drop shot exponents on tour. Vondrousova, a quarterfinalist here in 2019, has won all three of their past encounters, but two of those have gone the distance - including a 6-2, 4-6, 6-4 win in Dubai qualifying last month.