Andy Murray's former coach Brad Gilbert has admitted there were tensions in his relationship with the British No1, but has backed his former charge to achieve "great things".

The Lawn Tennis Association employed the American - whose previous proteges included Andre Agassi and Andy Roddick - to take the Scot to the next level but Murray dispensed with his services before the end of the LTA contract.

Gilbert admitted there were flashpoints with 21-year-old, who takes on France's Michael Llodra in the second round of the US Open later today, but for most of the time the pair had a happy working relationship.

"The day before I started coaching Murray, I didn't know him at all," Gilbert told The Guardian today. "There was a big culture difference - it was the first time I had coached a non-American.

"Andy is argumentative if he feels strongly about something. A lot of people in his team gave in to him. I didn't so we would argue, about sports mostly."

But despite conceding the problems which existed in his dealings, Gilbert has enjoyed Murray's surge into the top six of the world rankings and believes he has the ability to become a first-class player.

Gilbert added: "He is now doing a lot of things I was asking him to do. Great things are going to happen to him."

Meanwhile, world No8 Roddick produced a serving masterclass to begin his quest for a second US Open title with a 6-2, 6-2, 6-2 victory over Fabrice Santoro, of France.

Third seed Novak Djokovic overcame an ankle injury to defeat Frenchman Arnaud Clement 6-3, 6-3, 6-4 while fifthseeded Russian Nikolay Davydenko beat Israel's Dudi Sela.

Seeds Nicolas Almagro, Jo-Wilfried Tsonga, Dmitry Tursunov, Radek Stepanek and Marin Cili also advanced.