MIAMI (AFP, REUTERS) - Australian women's tennis world No. 1 Ashleigh Barty saved a match point as she battled back to defeat Slovakia's Kristina Kucova on Thursday (March 25) and reach the third round of the ATP and WTA Miami Open.

Top-seeded Barty, the 2019 Miami champion and French Open winner, dispatched 149th-ranked Kucova 6-3, 4-6, 7-5, advancing to a match with another Grand Slam winner, Latvia's 54th-ranked Jelena Ostapenko who beat Belgian Kirsten Flipkens 6-2, 5-7, 6-3.

Barty fired 15 aces, two in a rally from 0-40 down in the ninth game of the final set, to defeat Kucova after two hours and 27 minutes.

"There's nothing like coming through a test like that," she said.

"It was important in that match to stick to working and trying to figure it out as I went on. (I'm) just really happy I never gave up and happy I gave myself a chance to stay in the hunt."

The 24-year-old Aussie avoided her first three-match losing streak since 2014 after having fallen to Czech Karolina Muchova in last month's Australian Open quarter-finals and American Danielle Collins at Adelaide the following week.

Kucova, whose only win over a top-10 foe came five years ago, forced a third set after Barty sent a forehand long to surrender the lone break of the second set.

In the third, Barty sent a backhand wide to give Kucova a break in the fourth game and a 3-1 edge and they both held serve until Kucova served for the match leading 5-3.

On Kucova's only match point, she missed a weak first serve and Barty smashed the second for a down the line winner.

Kucova sent a backhand long two points later to surrender a break and Barty held then broke for a 6-5 edge only to make three errors to put herself one point from a tie-breaker.

Instead, Barty blasted back-to-back aces up the middle and a backhand winner then swatted a service winner on her first match point for the triumph.

"Mentally you need to stay there to give yourself a chance," Barty said. "I was proud I was able to hang in there when mentally I could have gotten a little loose."

Only Japan's second-ranked Naomi Osaka can overtake Barty for the world No. 1 spot at Miami.

Osaka, who won her fourth Grand Slam title at the Australian Open in February, launches her campaign on Friday in a second-round clash with Australian Aja Tomljanovic.

Third-seeded Simona Halep struggled early but stormed home for a 3-6, 6-4, 6-0 victory over France's Caroline Garcia.

The two-time Grand Slam champion from Romania, ranked third in the world, was playing her first match since a quarter-final loss to Serena Williams at the Australian Open.

After Garcia pocketed the first set with an ace on set point, she broke Halep to open the second and saved three break points to extend her lead to 2-0.

But Halep regained the break to knot the set at 3-3, and after breaking Garcia again in the 10th game roared through the third set.

Swiatek, Kerber advance

In other women's second-round action, reigning Roland Garros champion Iga Swiatek beat Barbora Krejcikova 6-4, 6-2, and former world top-ranked Angelique Kerber of Germany steamrolled qualifier Renata Zarazua 6-0, 6-0.

"The score, it's a little bit different than the match was, because (a) few games were really close and tough," said Kerber, who next faces another former world No. 1 in Victoria Azarenka.

The Belarusian advanced by walkover after a knee injury forced Laura Siegemund to pull out of their scheduled match.

Men's seeds swing into action on Friday, led by top-seeded world No. 2 Daniil Medvedev, who takes on Chinese Taipei's Lu Yen-Hsun in the second round.

Russia's Medvedev, runner-up to Novak Djokovic at the Australian Open, overtook Rafael Nadal for No. 2 in the world after his triumph in Marseille earlier this month.

On Thursday, British teenager Jack Draper's ATP Tour debut ended abruptly after he collapsed on court during his first-round match against Kazakhstan's Mikhail Kukushkin.

The sunny, humid and hot conditions on Court 2 appeared to have taken a toll on the 19-year-old wild card during the first set which lasted 81 minutes.

With Kukushkin leading the set 6-5, Draper appeared distressed and he had his heart rate checked courtside by medical staff before deciding to continue. His return was short-lived as he fell to the ground while attempting to keep the ball in play on set point, rolling onto his back as medical staff quickly came to his aid.

With Kukushkin sealing the set 7-5, Draper retired. "At the changeover, I was starting to feel my body a bit," said Draper. "I said that I'm going to carry on because I wasn't feeling faint... But obviously when I got out there, that wasn't the case.

"On the last point, I didn't collapse. I actually just tripped because I was starting to feel really dizzy and stuff."

Draper had an ice pack placed on his neck at the end of the first set before he walked off court. "In the last couple of hours, I have been with physios, trying to recover as best as possible, just trying to look after myself and move forward."

Meanwhile, three-time Grand Slam champion Stan Wawrinka faces a few weeks on the sidelines after having an operation on his left foot for a niggling problem.

"After having some problems in my left foot for a while, I have decided to do a small procedure on it," the 35-year-old Swiss said in a tweet on Thursday accompanied by a picture of him on a hospital bed.

"Everything went well. I will be out for a few weeks but can't wait to start practising again soon."

Wawrinka underwent knee surgery following his last ATP title in 2017 and had trouble with injuries through 2018, during which his ranking fell to 263. He is currently ranked 21st.