In a statement on Saturday, Channel Nine said Lyon, who is also the co-host of Footy Classified, a Triple M commentator and is an Age columnist, had been "suffering from a serious mental health condition".

Nine said there was no time frame as to when he would return to television.

The network's managing director, Ian Paterson, said Lyon, also a Melbourne Football Club great, had his full support.

"We are all supporting Garry and hope he will be back to good health very soon. Our priority is his wellbeing," Paterson said.

"Garry has our full support. From here on, it's a private and personal matter and we ask that be respected."

The Footy Show returns next month, most likely on March 23. James Brayshaw will host the show solo until Lyon returns.

Nine said journalist Damian Barrett would fill in for Lyon on Footy Classified, which also features The Age's Caroline Wilson.

Lyon will also stop providing a weekly column for The Saturday Age during his recovery.

It has been reported Lyon and good friend Billy Brownless, who also appears on The Footy Show and have worked together for at least 15 years, have fallen out over a personal matter. The two families had also been close, with Brownless' former wife, Nicky, and Lyon's wife, Melissa, best friends.

Brownless is understood to be rocked by the issue, and believes his friendship with Lyon is all but over.

Lyon's manager Craig Kelly, of Elite Sports Properties, did not wish to comment.