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."
More top news
A couple from Tennessee got a wedding video with a difference when their dog filmed their "magical" day via a GoPro camera.
The Queen will return to Malta, where she once lived more than 60 years ago, tomorrow. Here is a look back on her time there.
After a quiet night, a fine, bright start tomorrow with the best of the sunshine through eastern counties.