Aussie tennis legend Paul McNamee has dismissed Rafael Nadal's chances at the Australian Open, declaring the Spanish superstar will only be a genuine Grand Slam contender at the French Open.

Nadal, 36, is desperate to defend his men's singles crown at Melbourne Park later this month - but McNamee will be stunned if the veteran snares his 23rd career major.

The prominent sports administrator, who served as tournament director of the Hopman Cup and was a previous CEO of AFL club Melbourne Demons, also stated Nadal has 'lost a yard' of speed and isn't the same threat on court.

Recent defeats to Britain's Cam Norrie and Aussie Alex de Minaur at the United Cup when representing Spain has other players on the ATP circuit confident they will have Nadal's measure come January 16, according to McNamee.

'Like (Roger) Federer before him, Nadal is battling injuries. In 2022, he had an abdominal tear, ruling him out of a Wimbledon semi-final against Nick Kyrgios,' McNamee said in his Sydney Morning Herald column.

'Plus there was a recurrence of a chronic ankle injury, and he has long battled tendonitis in the knees.

'Court coverage has always been a major asset of Nadal's but, and this is a cruel thing to say, I fear he's lost a yard.'

McNamee wasn't totally scathing - he went onto label the Nadal forehand the 'single best shot in the history of tennis', better than the Pete Sampras or Roger Federer serves, or the Novak Djokovic backhand.

He is tipping Nadal to again win at Roland Garros later this year, but pointed to the likes of world No.1 Carlos Alcaraz, fellow young gun Jannik Sinner, Felix Auger-Aliassime, Stefanos Tsitsipas and Daniil Medvedev as ones to watch at Melbourne Park.

The two-time Wimbledon doubles champion also is anticipating 'big runs' from local hopes Nick Kyrgios and de Minaur.

Djokovic - who has won the Australian Open a record nine times - looms as a genuine contender, despite turning 35 last May.

The Serbian, with 21 Grand Slam titles to his name - will also be highly motivated after his visa was cancelled 12 months ago due to not revealing his vaccination status.

He was later sent home by the Australian government in scenes which generated international headlines.