TENNIS US OPEN: THERE WAS a gorgeous moment after Andy Murray had hit a particularly imperious double-fisted backhand down the line under the floodlights in the Arthur Ashe stadium here on Monday evening when his coach, Miles Maclagan, flicked his eyebrows in an expression of "where the hell did that come from?" surprise.

This 6-1, 6-3, 6-3 fourth-round victory over Switzerland's Stanislas Wawrinka, the world number 10, and Olympic doubles gold medal winner with Roger Federer, was as near perfection as Murray has ever achieved at grand slam level.

Murray quite clearly believes that today, when his quarter-final will switch from night to sunshine, he can achieve something similar against Argentina's Juan Martin del Potro, currently in the middle of the richest vein of form in his teenage life.

"He doesn't miss a whole a lot and he moves pretty well for a big guy," said Murray. "But when you watch him I don't think that you see anything that's unbelievably special."

If this sounded as if Murray was damning the 6ft 6in Argentinian with faint praise then it would not be too far from the truth.

The two have met only once before, at the Italian Open this year, when the Argentinian retired with a back injury, although not before a minor altercation sparked by Del Potro when he drilled a ball at Murray, refused to apologise, and then made remarks about his mother, Judy, who was there supporting him.

"I haven't spoken to him since, but for me it's another tennis match. When you get on the court you've got to put your emotions aside and get the job done. Whether I like Del Potro or not really doesn't make any difference," said Murray whose professionalism and maturity have increased markedly this year.

There will be blips both on and off the court, but here is a British player resolute in the belief that he can win a grand slam title. And, unlike Tim Henman, he has the ability and game to back it up.

This win lifted him to a career-high number five, making it virtually certain, barring injury, that he will be in Shanghai later this year for his first appearance in the end-of-season Tennis Masters Cup, limited to the world's top eight players.

The gap between him and Rafael Nadal, Roger Federer and Novak Djokovic remains considerable, although he has twice beaten the Serb this summer, and holds a 2-1 career advantage over Federer.

At Wimbledon, after defeating France's Richard Gasquet over five sets in the fourth round, he never remotely looked like defeating Nadal.

"I got killed. He played way too good for me, but I feel like I'm playing better now. I'm definitely going to be more rested this time round and hopefully play a better match."

Should he defeat Del Potro then Nadal may be his semi-final opponent, though for now all thoughts are focused on the Argentinian who since an early exit at Wimbledon has won four tournaments in succession.

His 6-3, 6-4, 6-3 fourth-round victory over the 18-year-old Kei Nishikori, the first Japanese man to reach the last 16 of this tournament since 1937, extended his unbeaten run to 23.

"I've known him since we were juniors," said Murray. "I wasn't really great friends with him before, and I don't need to be now."

The most impressive aspect of Murray's win over Wawrinka was the way he took control. The Swiss was nervous and Murray rarely allowed him a whiff of sustaining oxygen. His groundstrokes were stunning and the 24,000 crowd could only admire what they saw.

"I'd been looking forward to playing my first night match in the Arthur Ashe for a long, long time, and then to play like that made it pretty special," he said.

"It is such a huge stadium that there is always a buzz. I loved every minute of it."

Several times Murray gazed up at the giant electronic scoreboard as the replays were shown. "I think most players watch. They normally only show good points, so that's why," Murray smiled. He had good reason too, and will hope to again against Del Potro today. "I think I'm playing well enough to win."

If he can replicate his performance against Wawrinka then it seems altogether likely.

Guardian Service