"We have been concerned about our player stocks for some time, particularly the French market, but there's a bit going on in England and Japan as well," Tew said. "There's been more heat than there has ever been.
"Clubs are increasingly talking to agents about players at a much younger age. Unfortunately it is getting younger and younger to a point we are going to have sit down to make sure we are not talking to young men before they are ready to make those type of decisions. It is teenagers, sometimes 15-year-olds, being approached about signing by clubs in both union and league. That's scary. We have to be very careful."
Some of those who leave New Zealand shores will end up playing against the All Blacks. In the last round of Six Nations matches, every country had at least one New Zealand born player within their matchday squad.
World Rugby has extended the residency qualification period for international players from three to five years effective from 2020, however Tew believes this may have caused clubs to target even younger players.
"With the five-year eligibility rule coming in that may or may not help," Tew said. "We may see them target younger players even earlier and try to qualify them for the five years. What we are seeing at the moment is younger players being offered longer contracts. It is an ongoing conundrum without a straightforward solution in a free market. As bad as it is for New Zealand, it is a hell of a lot worse for Samoa, Fiji and Tonga.
"It is a concern to us, but it should also be a concern to those [foreign] unions too because we are seeing foreign players filling up a number of critical positions within teams and leagues. In the long term that cannot be good."
Unlike its counterparts in Australia and South Africa, NZR refuses to pick overseas-based players. As an alternative, Tew is exploring the possibility of opening relationships with certain foreign clubs where NZR would send players for sabbaticals. That would allow the player to maximise their earnings while NZR can monitor their development and ensure their return to the fold. Tew has mentioned Harlequins as a possible example.
"We are talking to a number of clubs over an extended period of time with connections to New Zealanders who we know are there," Tew said. "It may just be another piece of the jigsaw so players can go to clubs where we have connections with and that will help us stay in touch."
If Tew is unnerved by the continuing exodus of players, then he is a lot calmer about the "brain drain" of New Zealand coaches. Chris Boyd has become the latest Kiwi coach to announce his departure when he swaps the Hurricanes for Northampton later this year. Dave Rennie, Todd Blackadder, Jamie Joseph and Tony Brown have also flown the nest in recent years, but Tew says that NZR keeps tabs on all its foreign based coaches including Warren Gatland and Joe Schmidt.
"The key thing is communication and making sure they know what is going on," Tew said. "If they want to come on then the transition can be made as early as possible. We spoke to Warren last year both in Cardiff and New Zealand. We are not strangers. He has a son playing in New Zealand. Joe is also someone a number of us know and respect.
"Wayne Smith, Steve Hansen and Graham Henry all coached in Europe and came back and made a huge contribution to the era we are currently experiencing.
They deepened their experiences going to another viewpoint.
"We would like to keep more coaches here, but the reality is that we do not have enough roles to keep them all content. Rugby is such a fast moving beast that while there will be some systems and experiences that you can take with you, but most teams move on very quickly."
