WASHINGTON -- World number one Ashleigh Barty of Australia and seventh seed Aryna Sabalenka of Belarus each fended off match points before outlasting their tough opponents in second-round epics at the Miami Open on Thursday.

Barty overcame qualifier Kristina Kucova of Slovakia 6-3, 4-6, 7-5 in two-and-a-half hours, while Barty was forced to save one match point while down 3-5 in the third set, in the midst of reeling off the final five games of the clash.

"Never give up, never ever give up. You're always in there with a chance," said Barty. "Today was really hard work, and I enjoyed every single minute of it. There's nothing like coming through a test like that, and now I get another opportunity in a couple days time to play another tough match, and test myself again."

Sabalenka, meanwhile, staved off two match points in the decisive final-set tiebreak before quashing the challenge by qualifier Tsvetana Pironkova of Bulgaria 0-6, 3-6, 7-6(9).

"Since a young age, my parents keep telling me, 'It doesn't matter what goes on in the court, you just have to fight, and if you will fight, you will get the wins.' That's what I did today," Sabalenka said.

Elsewhere, third seed Simona Halep from Romania and fifth seed Elina Svitolina from Ukraine both reached the next round after three-set battles.

Chinese number one Wang Qiang lost to Marketa Vondrousova of the Czech Republic 6-4, 6-4.