Cahill, who has previously coached stars such as Lleyton Hewitt, Andre Agassi, Simona Halep, and Andy Murray, did not hesitate to name Djokovic as the undisputed greatest.

Roger Federer and Stan Wawrinka shrugged off the threat of rain to storm into the U.S. Open semi-finals on Wednesday, while Simona Halep stood up for the younger generation to complete a women's ...