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.