Murray uses friendly fire to warm up for Wawrinka

Briton faces first big test at US Open with help from an old acquaintance and determination to succeed

He may be without a permanent coach following his split with Miles Maclagan, but Andy Murray is not exactly short of support here at the US Open. The 23-year-old Scot's entourage all but filled his player box during his straight-sets victory over Dustin Brown on Friday night.

After a place in the third round had been secured, Team Murray's work was far from done. Judy Murray went off to watch her son's next opponent – he will meet Stanislas Wawrinka, following the world No 27's victory over Juan Ignacio Chela – while Alex Corretja and Daniel Vallverdu joined Murray on the practice court. The 85-minute victory over Brown featured so few rallies that Murray just wanted to hit some more balls.

Corretja has been a part-time member of the world No 4's coaching team for the last two years – it was a disagreement over his role that led to Murray parting company with Maclagan – while Vallverdu has been a friend since their teenage days together at the Sanchez-Casal academy in Barcelona.

The Venezuelan, who has played doubles with Murray in the past, has been an important figure in his camp this summer. He was a hitting partner last month at the Masters Series tournaments in Toronto and Cincinnati and he has been having his say on tactics, although he is not expected to become a permanent member of the Scot's coaching team.

"He's my best friend," Murray said. "He's known me since I was 15. We used to play doubles together. He knows my game well. He watches all my matches on the TV. He knows me well as a person. It's nice to have someone like that around. It's nice to have friends and family around. I wouldn't say he is coaching me. He's just here to help out. I've hit with him every single day since I've been here. He's a very good player."

Vallverdu also went to have a look at Wawrinka. "He'll try to get some tactics, some tips," Murray said. "He knows tennis. He was the No 1 player at the University of Miami. He was No 3 in college tennis. He played Davis Cup for Venezuela. He was a good junior player too."

Murray said he found it hard to assess his form on the basis of his match against Brown, but had been pleased with the way he had beaten Lukas Lacko in the opening round. Having not played his first match until Wednesday, he was happy to have won quickly on both occasions. "It's a good start but the matches get tougher from now," he said.

Wawrinka, who works with Roger Federer's former coach, Peter Lundgren, has won three of his eight matches against Murray, though two of those victories have been on his favourite surface, clay.

Their last two meetings have been in the fourth round of Grand Slam events and Murray has won on both occasions. The Scot triumphed in straight sets on his way to the final here two years ago but he was taken to five sets before winning last year at Wimbledon, in the first match to be played under the Centre Court roof.

"It was my best match for sure," the 25-year-old Wawrinka said, after his 7-5 6-3 6-4 victory over Chela. "It was a great experience – the first night session at Wimbledon with the roof on. It was really a great match even if I lost."

How would he go about trying to beat Murray now? "I need to stay very aggressive with my game and especially the serve. He's very good in defence, but I think I need to take the ball early and come into the net.

"He has a great serve, but he is playing far away from the baseline and I think that's where I need to go, to keep him far away from the baseline."

Murray described Wawrinka as "a very, very difficult player" and added: "He's had a lot of close matches with top players before so I'm going to have to play very well to win that one."

What did Murray see as Wawrinka's main attributes?

"He does everything well," he said. "He serves well. He's got a solid return. He can obviously play good doubles. He's won the Olympics with Roger [Federer], so he can volley well. He plays good. He doesn't have one massive weakness so I'm just going to have to play a little bit better than him. I'm going to have to serve well, go for my shots."

Murray is determined to continue playing the more attacking game that served him so well last month in Toronto, where he won his first title for nine months. "I need to play my game," he said. "I need to play aggressive when I get the chance. I've been serving well the first couple of matches and it's a lot easier to play aggressive when you're serving well."

Reaching the last 32 here extends Murray's excellent record at the Grand Slam tournaments. He has reached the third round or better of the last 11 tournaments, dating back to his first-round defeat at the Australian Open in 2008, and he arrived here as the only player other than Federer to have reached the fourth round of the last nine Grand Slams.

Should he beat Wawrinka, Murray will next play either Sam Querrey, who beat him in the Las Vegas final at the start of the US hard-court season, or Marcel Granollers.