Miami Open: Ailing Rafael Nadal retires as Stan Wawrinka, Petra Kvitova fall

Ailing Rafael Nadal, struggling to cope with heat and humidity, retired from his second-round match on Saturday at the ATP and WTA Miami Open, handing 94th-ranked Bosnian Damir Dzumhur a 2-6, 6-4, 3-0 triumph.

Two-time Grand Slam champions Stan Wawrinka and Petra Kvitova also crashed out of the hardcourt event, but it was 14-time Grand Slam champion Nadal`s exit that proved most stunning of all.

Miami Open: Ailing Rafael Nadal retires

The Spanish fifth seed, a four-time Miami finalist but never a champion, was also a first-match loser at the Australian Open, only the second Grand Slam opener defeat of his career.

Dzumhur, 23, won 22 of the last 29 points as Nadal, 29, repeatedly spoke with a trainer and searched for solutions, asking for his blood pressure to be taken after two games of the third set.

"Can we not check the tension, if it is good or bad please?" he said. Told it was good, he said, "Continue."

After dropping the third game, he sat with his head down as a trainer told him, "If you`re feeling bad, there`s no point to continue."

Nadal battled through three more points and finally said he could not go on.

"Definitely I want Rafa to recover," said Dzumhur. "He`s one of the best players in tennis and I wish all the best for him."

Nadal squandered nine break-point chances before Dzumhur held in his first service game of the match. But the Bosnian double faulted away the last three points in the fourth game to surrender a break and Nadal broke him again to finish off the set.

Dzumhur broke Nadal in the third game of the second set but netted a forehand in the eighth game to pull the Spaniard level at 4-4. But the Bosnian responded by breaking back for a 5-4 lead, fist pumping after a backhand winner to claim the game, and held at love to force a third set.Swiss fourth seed Wawrinka, who has won titles this year at Chennai and Dubai, was ousted by Russia`s Andrey Kuznetsov 6-4, 6-3 while Czech eighth seed Kvitova, the 2011 and 2014 Wimbledon winner, fell to Russian 30th seed Ekaterina Makarova 6-4, 6-4.

"I just tried to keep the pressure on him," said Kuznetsov, who fired 23 winners and seven aces to advance in 79 minutes.

Wawrinka, the 2014 Australian Open and 2015 French Open champion, managed only 16 winners against 37 unforced errors and went 0-for-8 on break point chances.

Kuznetsov, ranked a career-best 51st, avenged a third-round loss to Wawrinka earlier this month at Indian Wells and made the Swiss his highest-ranked beaten foe.

With Nadal and Wawrinka out, the top-ranked player in their quarter of the draw is Canadian 12th seed Milos Raonic, who is coming off a runner-up showing at Indian Wells. He beat American Denis Kudla 7-6 (7/4), 6-4 and next faces US 22nd seed Jack Sock, who advanced 6-2, 3-2 when Ukraine`s Sergiy Stakhovsky retired with a back injury.Japanese sixth seed Kei Nishikori advanced to the third round by downing 107th-ranked French qualifier Pierre-Hugues Herbert 6-2, 7-6 (7/4).

The 26-year-old Asian star, runner-up at the 2014 US Open and coming off a fourth consecutive title last month at Memphis, denied the Frenchman on two set points in the ninth game of the second set and took four of the last five points in the tie-breaker to win after 88 minutes.

"He played much better in the second set," Nishikori said. "I tried to be aggressive. I knew I had to somehow give him some pressure. I stayed confident even a break down and had a good win."

Next up for Nishikori, who could meet Britain`s Andy Murray in a quarter-final, is Ukraine`s 27th-seeded Alexandr Dolgopolov, a 6-4, 6-4 winner over Italy`s Andreas Seppi.

Murray and women`s world number one Serena Williams were scheduled to compete in later matches.

Polish third seed Agnieszka Radwanska reached the last 16 by beating American Madison Brengle 6-3, 6-2 while Romanian fifth seed Simona Halep downed Germany`s Julia Goerges 6-4, 6-1, to book a last-16 matchup with British wildcard Heather Watson, who outlasted Belgian Yanina Wickmayer 3-6, 7-5, 6-3.