Five-time champion Roger Federer was sent out of the U.S. Open after being defeated by Australia's John Millman on Tuesday.
Millman defeated Federer 3-6, 7-5, 7-6, 7-6 in the Arthur Ashe Stadium in New York.
The 29-year-old will play against Serbia's Novak Djokovic in the quarter-final.
Sharapova loses against Suarez Navarro
Former champion Maria Sharapova was defeated in the fourth round by Spain's Carla Suarez Navarro.
Navarro advanced to the U.S. Open quarterfinal with straight-sets win against Sharapova at 6-4, 6-3.
It was Sharapova's first U.S. Open since the end of her doping ban.
"She played really well. There's a lot of things she did well. I thought in today's conditions, her ball was getting up on me a little bit more, much more than my previous three opponents that I played," Sharapova said after losing the game.
"I know that Maria plays every day here. For me it's totally different, so I'm really happy because I played a really good match. I really enjoyed this crowd, this amazing night session," Navarro said after the match.
