New York, United States: World number one and defending champion Rafael Nadal raced into the third round of the US Open on Wednesday with a straight-sets win over Vasek Pospisil.
In a match where the 25-second serve clock provided much of the drama -- with both players receiving time violation warnings - 17-time Grand Slam champion Nadal triumphed 6-3, 6-4, 6-2.
He'll fight for a place in the last 16 against Karen Khachanov, the 27th-seeded Russian who beat Lorenzo Sonego 7-5, 6-3, 6-3.
"The conditions are tough," Nadal said. "It was important to start very well with that break. To win in straight sets is always very positive, especially in these conditions. It's almost midnight, very happy about the victory."
Third-seeded Argentinian Juan Martin Del Potro, who career was nearly ended by wrist injuries after his maiden Grand Slam triumph here, defeated American Denis Kudla 6-3, 6-1, 7-6 (7/4).
Del Potro was delighted to get through in three sets, and not spend too long in the steamy sunshine.
Organizers again implemented an extreme heat policy that allowed both men and women a 10-minute heat break in matches extended beyond straight sets.
Stefanos Tsitsipas, the Greek 20-year-old who came in with high expectations after beating four top 10 players en route to the Toronto Masters final, said the heat took a mental as well as physical toll.
"You don't have fresh air to breathe -- you breathe this heat that's coming, the moisture that's in the air. So you feel like you are empty," said the 15th-seed, who fell 6-4, 6-3, 4-6, 6-3 to Russian Daniil Medvedev.
Medvedev, who won his second ATP title of the season at Winston-Salem last week, booked a third-round meeting with 20th-seeded Croatian Borna Coric, a 7-6 (7/4), 6-2, 6-3 winner over Spain's Roberto Carballes Baena.
Fifth-seeded South African Kevin Anderson, runner-up to Nadal last year and a runner-up to Novak Djokovic at Wimbledon, made quick work of France's Jeremy Chardy, 6-2, 6-4, 6-4.
Anderson next faces rising Canadian star Denis Shapovalov, who laboured to a 6-4, 4-6, 5-7, 7-6 (7/2), 6-4 victory over Italian Andreas Seppi.