Top-seeded Angelique Kerber of Germany and 11th-seeded American Venus Williams advanced with third-round victories, but eighth-seeded American Madison Keys was an upset victim in Sunday's action at the Miami Open.
Kerber got off to a rocky start, losing the first three games to American Shelby Rodgers, but the world's No. 1-ranked player rallied to win that set. Kerber then came back from a 4-2 deficit in the second set to complete a 6-4, 7-5 victory.
"It was a good match," Kerber said. "I was trying to feel my game again. I was moving good, but it was not so easy because she didn't play badly. I was trying to stay positive and play my tennis.
"It's always good to have close sets, especially when you win them at the end because they give you confidence that you can go out in your next match knowing you can win close matches because you've just done it a day ago. I'm looking forward to the next match."
Up next for Kerber is Japanese qualifier Risa Ozaki, who defeated Julia Goerges of Germany 7-6 (5), 6-3.
Williams recorded a decisive 6-3, 6-0 victory over Romania's Patricia Maria Tig.
"I felt like my level was continuing to rise, which is exactly what I want," Williams said. "It was just one break of serve in the beginning; I'd never played her, so you always have to get used to new patterns and rhythm.
"I thought she played well and has a great game; every game was competitive."
Williams' next opponent is seventh-seeded Russian Svetlana Kuznetsova, who eliminated American qualifier Taylor Townsend 6-4, 6-2.
"I know her game, and I don't think there'll be any surprises," Williams said of Kuznetsova. "She knows mine. I'll continue to control the court, and that's what I'll try to do."
Third-seeded Simon Halep of Romania had little trouble against Estonian qualifier Anett Kontaveit, winning 6-3, 6-0.
Elsewhere, Lara Arruabarrena of Spain upset Keys 7-5, 7-5.
Keys had 10 break-point opportunities in the first set, but she let all 10 slip away. Keys had three set-point chances on Arruabarrena's serve in the 10th game, but could not convert any over them, then lost her serve for the first time in the 11th game. Keys had two more break opportunities in the 12th game before Arruabarrena finished the first set on her first set point.
Keys then bolted to a 3-0 lead in the second set but could not continue the momentum. After Keys lost her serve for the third time in the set to give Arruabarrena a 6-5 lead, the Spaniard served out the set, winning on her first match point.