Former All Blacks coach Steve Hansen has labelled Sonny Bill Williams the greatest athlete he's ever worked with.
Hansen's comments come on the eve of Williams' return to the NRL after a six-year absence, with the dual-code international set to come off the bench for the Sydney Roosters in their clash against the Canberra Raiders.
Williams is set for a limited minutes role as he eases his way back into action, having not played any competitive matches since early March, for Toronto Wolfpack in the English Super League.
The 35-year-old will see out the remainder of the NRL season with the Roosters, before rejoining the Wolfpack for the final year of his contract.
During Hansen's time as a rugby union coach, he's worked with some great players, but he's adamant none of them compare to Williams.
"The greatest rugby player I've coached was [Richie] McCaw but Sonny would be the best athlete I've coached from a pure athlete sense," Hansen told the Daily Telegraph.
"Sonny is 35 now but he's been an active athlete for a long time and he really looks after himself. He's a freak of nature.
"There is no reason, as long as he stays injury-free, that he won't do the job. He had been out of league for a while before coming back and going to Toronto, but he's just such a good athlete.
"As he has got older, he has matured. His training habits and his off-field habits are world-class now. He will be a good role model for the young fellas in the club."
Hansen mentored Williams in the All Blacks in two separate stints between 2011 and 2019.
Williams began his professional sporting career in rugby league with the Canterbury Bulldogs in 2004.
The fact Williams is still playing today is remarkable, as he revealed to the Daily Telegraph that he was almost forced to retire from professional sport in 2010.
Williams said it was a mystery medical issue, but didn't go into any detail.
"I was told 10 years ago by a great orthopaedic surgeon that, 'I can get you to the 2011 World Cup but beyond that only God knows...' So I guess I am forever grateful to the most high for making these adventures and challenges possible. And only the creator knows when it will all end."