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
The airline apologised as holidaymakers face disruption following an IT outage on Saturday morning.
The Hollywood couple, who have been married for 17 years, said they still have "tremendous love and respect for each other".
Jared Kushner discussed the possibility of setting up a secret line of communication with Russia, according to US media.