Roger Federer has praised ATP executive chairman and president Brad Drewett for his contribution to tennis over the past 35 years.
The ATP Tour announced today that the 54-year-old will be stepping down from his position after being diagnosed with Motor Neurone Disease.
Federer put the Tour's success in 2012 down to the "tremendous" work of Drewett, who he described as a "good friend".
"Brad has become a good friend of mine over the years and this is very sad news for all of us at the ATP and the entire tennis community," said Federer.
"He is well liked and respected by everyone and has done a tremendous job in leading the ATP over the past 12 months, overseeing some major initiatives and a record-breaking year in 2012.
"His dedication and service to the sport over the years has been truly admirable and he has been a central figure in helping to grow the ATP product across the globe.
"Our thoughts are with him and his family during this difficult time."
Drewett will continue in his role on an 'interim basis' until his successor is chosen by the ATP board of directors.
