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In an interview with Radio Sport's Daniel McHardy, Tew opened up on the increasingly "inevitable" prospect of All Blacks heading north and the concerning depletion of home-grown depth.
"There's no doubt the player market is as hot as it's ever been," said Tew. "The money coming out of Japan and France in particular is a bit concerning but there's no breaking news in that, is there?
"I think the money has increased in both those markets at least and there are some signs that it might heat up a bit in the UK too.
"At every level we're looking to retain the talent we want, from our sevens players right through to the top very experienced All Blacks.
"Inevitably some will move on and we know now that a number are going to after this World Cup and that is the inevitable cycle that we're now in."
With the Rugby World Cup being hosted in Japan this year, the Japan Top League will run two modified seasons in 2020, essentially offering a double payday to players.
The two-for-one prospect has made Japan a major player in the market, with All Blacks captain Kieran Read and teammate Ryan Crotty reportedly set to link up with Japanese clubs after the world cup. Several other All Blacks are also linked to similar moves.
Tew says this added quirk has caused "more trouble" with keeping players.
"A player can make a commitment to Japan and effectively get paid twice as much as they normally would in a 12 month period. [It's] not quite as simple as that but it's not far off. And that is causing us a little bit more trouble with some of the guys we would prefer."
Tew was however, excited about the potential development of a 12-team World League event, the brainchild of World Rugby vice-chairman Agustin Pichot. He sees it as a way to increase much-needed revenue for NZ Rugby, as it struggles to keep up with the financial might of the north.
"I'm going to Los Angeles this weekend for the next World Rugby meetings to discuss that ... pretty exciting times.
"If we can make better use of the test matches we already play for – and the view of everybody who's done some sort of research into that area suggests we can by being more meaning to it – then we will.
"We wanna look after our fans, we wanna look after our players, we wanna look after our competitive advantages, and we need to increase the revenue we've got. And all countries come to the table with similar expectations."