John McEnroe, 58, told Jimmy Kimmel two years ago that he believed he could still beat Serena Williams.
Australian Open: Roger Federer Beats Rafael Nadal To Capture 18th Grand Slam Title
Serena Williams Wins 23rd Major Title To Create Open-Era Record
Davis Cup: Rafael Nadal Leads Spanish Armada to Victory Over India
The French Open Win Has Definitely Sunk In: Rohan Bopanna