Two of the top six seeds, Sofia Kenin and Karolina Pliskova, lost Sunday in the round of 32 in the Miami Open.
Kenin, the fourth-seeded American, fell in three sets to Ons Jabeur of Tunisia, 6-4, 4-6, 6-4.
Jabeur, ranked 30th in the world, finished with 11 aces to none for Kenin, and she converted 80 percent of her break points to just 43 percent for Kenin.
The sixth-seeded Pliskova of the Czech Republic was beaten by the 29th seed, American Jessica Pegula, 6-1, 4-6, 6-4 in just over two hours.
The players were familiar with each other, having squared off in the past three tournaments, as well, and the outcome was the same as the other two matches: a win for Pegula.
“I played her a lot the last three weeks, three tournaments,” Pegula said in her news conference. “I kind of expected her to play well there. Even when I was up I still felt like she could easily come back just because she plays so aggressive and she serves well.”
Pegula took advantage on her second serve, winning 57 percent of those points to 32 percent for Pliskova.
Also falling was the 21st seed, Elena Rybakina of Kazakhstan. In a match that lasted just short of 2 1/2 hours, she lost to Sara Sorribes Tormo of Spain 6-1, 3-6, 6-2.
Sorribes Tormo said it was a matter of staying with her game against the powerful Rybakina.
“I still don’t believe it. When you play against this kind of player and they are hitting bombs, I try to stay all the time inside the court. Don’t lose the court, go against her, try to play as long as you can — it worked,” Sorribes Tormo said.
The second seed, Naomi Osaka of Japan, was ushered into the round of 16 when Serbia’s Nina Stojanovic withdrew before their match with an injury to her right thigh.
Among seeded players that stayed alive was Bianca Andreescu of Canada. The eighth seed battled American Amanda Anisimova, the 28th seed, for 2 hours, 44 minutes, and won 7-6 (4), 6-7 (2), 6-4.
The 12th seed, Garbine Muguruza of Spain, dropped the first set and needed 2 hours, 41 minutes to subdue Russia’s Anna Kalinskaya, 4-6, 6-3, 6-4.
“It was a very physical match, was a long match and a lot of ups and downs,” Muguruza said. “It was tough conditions with wind, so it was a lot about staying strong, staying strong in important moments.”
Also advancing was Elise Mertens of Belgium. In a battle of lopsided sets, the 16th seed defeated the 22nd seed, Anett Kontaveit of Estonia, 6-2, 0-6, 6-2.
Having perhaps the easiest time was 23rd-seeded Maria Sakkari of Greece, who needed little more than an hour to finish off Liudmila Samsonova of Russia, 6-0, 6-1.