The former coach of Dan Evans, who knocked the 11th seed out of the US Open, said it was clear from an early age that the British player had a natural ability.
The 23-year-old, who is ranked 179th in the world, clinched a 6-4 6-4 6-2 victory against Kei Nishikori in New York.
Scott Key told ITV News: "I think this a big opportunity for him to take on this as a big move forward in his career. Undoubtedly we all knew he had the talent but I think it's actually having the belief in his own talent and that's what's changing."
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After a relatively mild and quiet night, an episode of rain for many of us tomorrow.
The 34-year-old from Coulsdon in Surrey died during the private party in Headley in the early hours of Monday, Surrey Police said.
The Home Office made the arrests at various restaurants across London on July 4.