"I hold the ATP very close to my heart, and it's with sadness that I make the decision to enter this transition period due to my ill health," said the former world top-50 ranked tennis player.

"It has been a privilege to serve as executive chairman and president of the ATP, an organisation that I've been a part of for more than 35 years since I became a professional tennis player."

The 54-year-old Australian Drewett reached the quarter-final of the Australian Open at the age of 17 in 1976 and retired in 1990 before taking various roles within the ATP since being elected as an ATP Player Board Representative in 1993.

President of the ATP Player Council Roger Federer (right) has sent a message of support to ATP chief Brad Drewett (left) who is suffering from motor neurone disease

Messages of support have been sent from all over the world of tennis, including from one of the greatest players of all-time and the current ATP player council President Roger Federer.

"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," he said.

"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.

"Our thoughts are with him and his family during this difficult time."

World number four and 11-time Grand Slam winner Rafael Nadal also sent a message of support on Facebook.

"This morning I woke up with one of those news (sic) you'd never want to hear. Our friend Brad will leave the ATP to fight a terrible disease. He will always have us on his side with our support. Go Brad, be strong, we love you!"

Motor neurone disease, also known as amyotrophic lateral sclerosis (ALS) or Lou Gehrig's disease, is a neurological disorder which weakens muscles and goes on to affect movement, speech and breathing.

Drewett has stated that he will continue his role on an interim basis before the ATP director's find a replacement "in the near future".

Contact the writer of this story at [email protected]