Badosa, a former French Open junior champion, is the lowest-ranked player to beat Barty since September 2019.
Barty, the 2019 French Open champion, has held the No 1 ranking since September of that year, despite skipping the rescheduled US and French Opens in 2020 to remain in Australia.
It is a complicated way of calculating things, but in general, rankings points will remain part of a player's total for a minimum of a year and not more than two years.
The 24-year-old from Queensland elected not to travel outside Australia after the WTA Tour resumed last year, skipping both the US Open and the rescheduled French Open at Roland Garros in September.
Kim Clijsters only played three tournaments and three matches in 2020, beaten each time in the first round.
The 24-year-old Spaniard Sara Sorribes Tormo was in her first WTA final, and made it count.
Muguruza received a walkover into the title match after fellow former world number one Victoria Azarenka dropped out because of back pain
WTA CEO Steve Simon said in a statement that the tour is "currently reviewing if any further adjustments to the rankings process will be made."
Clijsters' comeback was disrupted by the coronavirus pandemic and she has yet to play in 2021. Miami will mark her first event since her first-round loss in the US Open in September.
Qatar Open: Former champions Karolina Pliskova, Petra Kvitova, Victoria Azarenka through to quarters
It was Jabeur who defeated the Czech during their last encounter in Doha in 2020 but this time it was 2017 Qatar champion Pliskova who booked her ticket to her first hard-court quarter-final since 2020 Dubai.
Keys hit 24 winners against 13 for the sixth-seeded Bencic, who was coming off a loss to Iga Swiatek in the final of the Adelaide International on Saturday.
Despite conceding the first set, Russia's Kuznetsova put up a spirited defence in the second leading to increasingly sprawling rallies with her well-matched Belarusian opponent.
Coco Gauff beat sixth-seeded Petra Martic 5-7, 6-3, 6-4 to advance to the quarter-finals of the hard-court tournament at Memorial Drive.
In Australia, Ankita Raina got her much-awaited Grand Slam debut and in the same week a first WTA Tour level win.
Ankita came from behind to beat the Italian 5-7, 6-1, 6-2 in the opening round of the USD 235,238 hardcourt tournament.
Kasatkina was the first winner of the new season, beating Wang Qiang 6-2, 3-6, 6-2 after trailing 2-0 in the deciding set. It was the Russian's first match since October, and Wang's first since March.
The world's leading tennis players are set to start arriving in Melbourne from 15 January and must undergo 14 days in hotel quarantine, although they'll be allowed to practice for limited periods daily in a bio-secure bubble.
Abu Dhabi WTA Women's Tennis Open 2021: Sofia Kenin 'happy to be travelling' as season starts in bio-bubble
Kenin, who is top seed in the year-opening WTA event in Abu Dhabi which starts on Wednesday, will be kept in a bubble along with her fellow competitors before they all move on to Melbourne for the delayed Australian Open.
Year in Review 2020, Biggest Sports Stories: Teenager Iga Swiatek wins French Open without dropping a set
Iga Swiatek became the first Polish player, male or female, to win a grand slam singles title when she lifted the Suzanne Lenglen trophy in Paris.
Pliskova published a photo on Facebook and Twitter featuring Bajin, fitness coach Azuz Simchich and a caption saying "Team Pliskova 2021".