US Open: Rafael Nadal in ominous form to cruise through to third round - and warns improvement is on the way

Spaniard believes the cooler conditions should improve the standard of tennis at the US Open

Rafael Nadal was in ominous form as he dispatched Vasek Pospisil to set up a third-round clash with Karen Khachanov at the US Open.

The defending champion took exactly two hours to clinch a 6-3, 6-4, 6-2 victory under the lights on Arthur Ashe Stadium, with the only moment of alarm coming in the second set when he dropped serve to trail 4-2.

But Nadal broke straight back and a run of four games in a row gave him the second set, with the third largely one-way traffic.

Nadal has played both his matches so far at night, when there is some respite from the searingly-hot conditions, although the humidity means temperatures have still been pushing 30C.

The world number one expects the level of tennis on show to go up as the temperature goes down, saying: "The good thing is I think things are going to improve the next couple of days.

"We'll be able to see, I think, better tennis than we saw the first couple of days of the US Open because playing under those conditions is, first thing, not healthy and, second thing, is not good for anybody: not good for the fans, not good for the players.

"The show is a little bit worse under these conditions."

Nadal was the biggest critic of the shot clock that has been introduced to count down the 25 seconds permitted between points but so far believes it is being implemented well.

Rafael Nadal was unhappy with a warning for exceeding the shot clock (AP)

He was given one warning in the third set but remonstrated with the umpire, claiming he hesitated because Pospisil indicated he was not ready.

Expressing disappointment that his Canadian opponent did not back him up, Nadal said: "Being honest, my surprise is that Vasek didn't came to the umpire and say, 'that's what happened'."

Nadal could have a sterner test in the next round on Friday against big-hitting Russian Khachanov, who defeated Lorenzo Sonego 7-5, 6-3, 6-3.

Rafael Nadal cruised through his second-round encounter with Vasek Pospisil (EPA)

The tournament lost one of its most talked-about names on Wednesday when 15th seed Stefanos Tsitsipas was beaten 6-4, 6-3, 4-6, 6-3 by in-form Daniil Medvedev, who won the Winston-Salem Open last weekend.

Greek Tsitsipas, with his flowing hair and one-handed backhand, has soared up the rankings this season and arrived in New York having beaten four successive top-10 players to reach the final of the Rogers Cup in Toronto.

But the 20-year-old could not summon the energy for another famous run, saying: "I kind of felt tired from the beginning of the tournament. I didn't feel the same fire inside of me.

"I did win the first-round match, but I did feel a bit empty. It's very annoying, because you really want to do well, but at the same time your body refuses to give 100 per cent."

Rafael Nadal will play Karen Khachanov in the third round at the US Open (EPA)

Former champion Stan Wawrinka reached the third round of a slam for the first time since before his knee surgery last summer, battling to a 7-6 (7/5), 4-6, 6-3, 7-5 victory over Ugo Humbert to set up a tasty third-round clash with Milos Raonic.

Wawrinka said: "My level is there. I'm playing really good tennis. I'm 33 years old, first time after big surgery that I'm pushing myself that much, but in general I think I did enough hard work to know and have confidence in my fitness."

Raonic defeated Gilles Simon in straight sets while there were also victories for third seed Juan Martin del Potro - who plays Andy Murray's conqueror Fernando Verdasco - Kevin Anderson, Dominic Thiem, John Isner and Denis Shapovalov, who overcame Andreas Seppi in five sets.

PA