Sara Sorribes Tormo fashioned a major upset Sunday at the Tokyo Olympic Games. The 48th-ranked Spaniard took down World No.1 Ashleigh Barty 6-4, 6-3 on Centre Court in Ariake Tennis Park.

Barty’s feet weren’t keeping pace with Sara Sorribes Tormo’s looping shots. Barty's forehand was misfiring, and she was making uncharacteristically poor shot choices. Despite saving two set points with backhand winners that caught the line, Barty dropped the first set – something that didn’t happen once in seven matches at the All England Club.

The second set was more of the same. Barty finished the match with 55 unforced errors. 

And so, the 25-year-old Australian and winner of a WTA-high 35 matches and four titles this season will have to try and win a medal in the doubles competition with partner Storm Sanders, where they are the No.6 seeds.

"I never really felt comfortable out there and wasn’t able to play the match on my terms," Barty said on the Olympic Channel broadcast afterward. "The key to my game is serving well and I wasn’t able to do that today. I was a bit erratic and made too many errors."

Sorribes Tormo, 24, was crafty, strategically hitting high-hopping shots to Barty’s backhand. Barty’s final unforced error gave Sorribes Tormo her third match point, and she converted it when Barty could only push a backhand into the net.

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Back in March, Sorribes Tormo won her first career title in Guadalajara. She has also reached two WTA 250 semifinals and the Miami quarterfinals. Sorribes Tormo improved her record to 21-12 for the season.

She’ll next face Fiona Ferro, who beat Anastasija Sevastova 2-6, 6-4, 6-2, in the second round.

“It was incredible I don’t know what to say; I still have goosebumps. It’s amazing,” Sorribes Tormo said afterward. “It’s the best victory in my career, for sure. Because of the place, for who she is, because of what the Olympics means to me and because of playing for Spain.”

It was a day when the top five seeds – and seven of the top – were all in action.

Osaka’s opening match was moved back to Sunday when the Tokyo Olympic Committee asked her to light a little fire under these Games – dropping the torch into the cauldron at the Opening Ceremony.

In her first match since withdrawing from the French Open after winning her first-round match on May 30, the No.2 seed looked like she’d never been away, cruising to a 6-1, 6-4 victory over  Zheng Saisai. Her first point back was an ace down the T.

With the loss of No. 1 seed Barty, Osaka – under the eyes of an expectant nation – is now considered by many the favorite to win gold.

Osaka won 28 of 32 service points and has now beaten Zheng three of four times.

Coming off a run to the Wimbledon final, No.5 seed Karolina Pliskova was in a hurry Sunday, ending Alize Cornet’s Olympics in the first round, 6-1, 6-3.

The 29-year-old from the Czech Republic was masterful, completing the day's first match in 63 minutes. She won 24 of 30 points on her serve. It was the fourth consecutive win for Pliskova over the 31-year-old from France.

Pliskova will next play Carla Suarez Navarro, who upset No.23-ranked Ons Jabeur 6-4, 6-1. The Spaniard is a cancer survivor, playing in her final season.

No.3 Aryna Sabalenka was almost as swift, sending home Magda Linette 6-1, 6-2 in 69 minutes. Sabalenka, who at Wimbledon two weeks ago reached her first career major semifinal, looked sharp.

She won 25 of 27 service points and broke Linette once in each set.

Sabalenka will play Donna Vekic, who beat Caroline Garcia in three sets, in the second round.

America’s best hope for a singles medal, No.11 seed Jennifer Brady, fell to Italy’s Camila Giorgi 6-3, 6-2. Giorgi broke the Australian Open finalist three times on her way to a second-round match against the winner between Jelena Ostapenko and Elena Vesnina.

In other action, No.7 Garbiñe Muguruza and No.10 Petra Kvitova also rolled to straight-set wins, while Argentina’s Nadia Podoroska advanced to the second round when Yulia Putintseva retired after losing the first set 7-6 (4) but leading 3-1 in the second.