Miami Open: Serena Williams sprints

Serena Williams in action against Zarina Diyas in their Miami Open third round match at Crandon Park Tennis Centre in Key Biscayne, Florida, on Saturday. Serena won 7-5, 6-3. (Photo: AFP)

Britain’s Andy Murray moved into the third round of the ATP and WTA Miami Open on Saturday but Rafael Nadal, dizzy as he struggled to cope with heat and humidity, retired from his match.

World number two Murray, twice a Grand Slam champion, downed Uzbekistan’s 76th-ranked Denis Istomin 6-3, 7-5 to reach the third round in a night match.

“That second set was tight but I managed to get through it,” said Murray, who next faces Bulgarian 26th seed Grigor Dimitrov in his quest for a third Miami crown.

Spanish fifth seed Nadal, a 14-time Grand Slam champion playing in the heat of the afternoon, feared for his safety and handed 94th-ranked Bosnian Damir Dzumhur a 2-6, 6-4, 3-0 triumph, stopping during a match for the first time in six years.

Two-time Slam winners Stan Wawrinka and Petra Kvitova crashed out of the hardcourt event, although Nadal’s exit proved most stunning of all.

Meanwhile, world no. 1 Serena Williams ousted Kazak Zarina Diyas 7-5, 6-3, in the match after Nadal and was also tested by the conditions.

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.

Wawrinka managed only 16 winners against 37 unforced errors and went 0-for-8 on break point chances.