The executive chairman and president of the ATP, Brad Drewett, has died at the age of 54.
Drewett had been at the head of men's tennis since the start of last year but it was announced in January this year that he was suffering from Motor Neurone Disease and stepping down.
A statement today read: "The ATP is deeply saddened to announce that Brad Drewett passed away at his home in Sydney, Australia, earlier today.
"Brad, who served as ATP executive chairman and president since January 2012, had been suffering from Motor Neurone Disease. Our thoughts are with Brad's family on this extremely sad day for them, the ATP and the entire international tennis community. He will be sorely missed by all."
Many professionals expressed their condolences on social media, with Rafael Nadal writing on his Facebook page: "A very sad [day] for the World of Sports and tennis in particular. Our president Brad has passed away. Rest in peace."
As a professional, Drewett made the quarter-finals of the Australian Open as a 17-year-old before going on to reach a career-high world ranking of 34 in 1984.