From Hugh MacDonald at Flushing Meadows

THEY were once the top double act in tennis and they have united in backing Andy Murray for a US Open title.

Andre Agassi and Brad Gilbert were the player and coach that dominated tennis for much of the nineties.

Agassi said this week that the 22-year-old Scot was his pick for Flushing Meadows. Gilbert, now a television commentator, agreed. After watching Murray thrash Ernests Gulbis in three sets, Gilbert, 48, said Murray, who he once coached, had matured.

"He was right there last year," he said of Murray's run to the 2008 US Open Final. "He might have been a little unlucky because he had to play second semi. But he's fitter and stronger so he is definitely in the mix."

Gilbert and Murray broke up in November 2007 after a turbulent relationship lasting just 16 months. But Gilbert believes Murray is physically and emotionally mature enough to win a Major. "Sure he is," said the man who coached Andy Roddick to a US Open in 2003.

"He is the closest one to knocking on the door," he said of Murray's attempt to win his first Major. "If you are knocking on the door, eventually you will go through the door."

Gilbert noticed a change in Murray when the Scot's serve was broken by Gulbis on Tuesday night. "Two years ago if Andy lost a service game like that he'd have blown a gasket and would have been yelling at me. Now he has learned to harness it and all you get from him is positive energy," he said.

"People ask me how can he be No.2 in the world when it doesn't look as if he does that much? I say that's his genius. He doesn't have to look that good to be that good. He can play for five hours now and that's what has taken him to the next level - all that working on his fitness. He's as fit as a fiddle."

The physical conditioning is crucial in a Major where matches can come hard and fast.

"Murray has positioned himself well," he said of the Scot's run of form that has included a Masters win in Montreal.

"The first week you can't win it, but you can lose it. The most important thing is to survive the first week," he said.

"The second week of this Major is the heaviest backload because you could potentially be playing five matches in seven days if you have the weather. It is most important to be efficient, get through it and take your chances in the second week."

Roger Federer, who beat Murray in the final last year, is also convinced that the Scot will be his biggest rival. The world No.1 said after defeating Simon Greul here: "Murray is definitely in the best shape of his life right now."

He added: "This year, with one more year of experience, he's definitely got a good chance to do well."

Murray, who plays Paul Capdeville of Chile in the second round tonight, is scheduled to meet Federer in the final again. The Scot was this week nominated by Andre Agassi, the US tennis legend, as the winner of this year's tournament. Federer said he was not irritated by Agassi's decision to go for Murray. "There are many experts and former players who have their picks. Not everybody can pick me, so that's fine," he said.

He added: "Andy deserves a few picks because he has played so well. The only thing is that he hasn't won a Slam yet, but he's still quite young. It's not like the guy is 35 years old. He's still got time."

Meanwhile, fifth seed Roddick moved a step closer to a potential semi-final date with Federer by blasting Frenchman Marc Gicquel away 6-1, 6-4, 6-4 and he will next face unseeded compatriot John Isner in the third round.

World No.4 Novak Djokovic claimed a 6-3, 6-4, 6-4 victory over Australian Carsten Ball.