Brad Gilbert sees Roger Federer as a clear favourite to win the Australian Open and said he can only "marvel at the greatness" of the 19-time grand slam champion.
Federer ended a five-year wait for an 18th major title at Melbourne Park last year, beating old foe Rafael Nadal in an epic final.
The Swiss icon went on to claim an eighth Wimbledon title in July, age proving to be no barrier for the world number two.
Gilbert, who has worked with the likes of Andre Agassi, Andy Roddick and Andy Murray in a successful coaching career, would not be surprised to see the 36-year-old defend his title in the first grand slam of the year.
The American told Omnisport: "It will be interesting to see how Novak [Djokovic] goes after what has been a very concerning injury and Rafa [Nadal] obviously had an amazing 2017, but Roger would be my clear favourite.
"Having seem him in action at the Hopman Cup, he was looking great.
"He is just amazing at the age of 36. Before the last couple of years he had never had time off, which is just incredible.
"He is a very young 36 and you just marvel at the greatness of such an icon. He is like a corporation with the way he plans his schedule, he is an amazing guy."
Federer will be up against Aljaz Bedene in the first round on Tuesday.
- Gilbert will be working in his role as an ESPN analyst at the Australian Open.
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