Roger Federer warned temperamental Australian Nick Kyrgios yesterday that he would never fulfil his potential without the work ethic to go with his talent. Kyrgios, 23, made another contentious exit from the Shanghai Masters on Monday after a running argument with the chair umpire who suggested his efforts were borderline. The 38th-ranked Kyrgios was on the end of a surprise first-round loss to the American qualifier Bradley Klahn, the world number 104 winning 4-6, 6-4, 6-3.

It is the third time in as many Shanghai appearances that Kyrgios has departed the Masters event under a cloud. Speaking in Shanghai, the Swiss great, 37, called Kyrgios a great player. But he also sounded a note of caution. "I think it's up to him where he wants to go and what his potential really holds," said the 20-time Grand Slam winner.