James Mortimer 08.Sep.2012
Williams, who departed New Zealand rugby as a World Champion All Black and Investec Super Rugby winning Chief, is now with the Panasonic Wild Knights, and Gosper told Reuters his presence there was in some respects a crucial investment - especially with the Rugby World Cup being in Asia in 2019.
Gosper didn't agree with critics who said the big money being spent on Williams would be better spent developing the grassroots.
"It (Williams time in Japan) is a kind of indirect way of doing it," the former chief executive of Europe, the Middle East and Africa for advertising giant's McCann Erickson.
"Particularly in Japan, where there is a love for the celebrity factor, I think he's a terrific injection of interest in the game in Japan.
"I think it's a great way to spend the money that they've spent. It's now up to Japan to take advantage of that wonderful opportunity of having him here."
Gosper, who recently complimented the Olympic movement for their effective marketing and evolution of the world's largest sporting event, said that Sonny Bill could be an ambassador in the same mould as football star Beckham.
"The game needs big stars," Gosper said.
"It's great for the game to have stars who are larger than the game almost, that are larger than life.
"Sonny Bill Williams is one of two or three people in the world - a little bit like David Beckham - who can capture the imagination, hearts and minds of young kids, mums, dads, a cross-section of the population.
"That generates interest in the sport as well."