All Black Beauden Barrett could be running right into a mega contract in either France or Japan.

New Zealand Rugby is digging in for the fight to retain All Blacks superstars Beauden Barrett and Brodie Retallick after the next World Cup.

But even they are not prepared to offer any assurances that their two most sought-after players can be retained to provide the experienced core for the next World Cup cycle through to 2023.

The international market, led by France and Japan, is simply at a level that NZ Rugby cannot hope to match. That, says chief executive Steve Tew, makes it increasingly difficult for experienced All Blacks to be re-signed so far out from the next global event.

NZ Rugby accepts there will be a post-RWC exodus of veteran figures following the global event in Japan next year. That's now a given in the four-year contracting cycle.

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That will likely see skipper Kieran Read, who has already confirmed his intention to finish up as an All Black after Japan, Ben Smith, Ryan Crotty, Waisake Naholo, Owen Franks, Sonny Bill Williams and Dane Coles depart. They have served their time and made their dues.

But it's that group of hardened experienced players still in their mid to late-20s who become important. Men such as Barrett, Retallick, Codie Taylor, Sam Whitelock, TJ Perenara, Sam Cane and Ardie Savea who could potentially go through to the next RWC.

"The money has gone up another notch which is predictable but disappointing," Tew told Stuff of the international market his organisation is constantly fighting. "We've always got a group of players coming off contract one way or the other.

"Clearly in Beauden and Brodie particularly, they're two world-class players who are worth a lot on the international market. So we're working closely with their people. But there's another bunch of young guys and more experienced players."

Asked if he was confident Barrett and Retallick could be retained, Tew's response during an extensive Saturday interview was deliberately qualified.

"I'm confident we'll do all we can to make their decision a tough one. We want them both to stay but we've got to be realistic about the market we're in too. So we'll have to wait and see."

Barrett might be the most difficult to hold on to. Clubs in France are reportedly ready to make him the highest paid player in the game at $2 million-plus a year and the deep-pocketed Japan companies are also said to be circling with similar offers.

The potential of combining a sabbatical-style stint in Japan with continuing his All Blacks career has been touted for Barrett, but it's thought the level of offers being waved under his nose could tempt him to make the move a more permanent one.

Retallick is likely to have different motivations but his status as the best and most consistent forward in the game will have French clubs offering the sort of money he might struggle to turn down.

GETTY IMAGES French clubs are circling to get their hands on a big man of Brodie Retallick's abilities.

Meanwhile, Tew was non-committal on the likelihood of rugby's radical league of nations concept getting over the line. A formal 12-team international competition has been mooted to replace the existing July and November windows, though at present it remains very much a work in progress.

"There's a concept being worked on, and we've all agreed it's worthwhile continuing that work. Until we get through that process and people sit back round a table and work out whether the change is going to make a difference … no decisions will be made," he told Stuff.

But Tew did confirm a change in the much-criticised international revenue model was not part of the process as it stood.

"This is not about discussing how the existing revenue is shared. We wouldn't even get to the table if that was the issue," he said.

"If we can increase the value of those games by putting them into a competition structure with some purpose then we'll increase the value broadcasters, sponsors and fans bring to it, then we can discuss how that extra revenue is shared.

"But that's a second body of work."

The long-time NZ Rugby boss was also not pushing any panic buttons about the All Blacks' late-season wobbles, with two test losses and another couple of near-misses.

SUPPLIED Beauden Barrett may be the toughest player for NZ to hold onto.

"We lost two tests in a 14-game programme and we probably feel as though it wasn't our best year. Most other countries would be pretty satisfied with that result.

"The international game is very competitive. We've always said the rest of the world weren't far behind and we needed to keep working hard to stay in front. That's still the case.

"But we absolutely pay tribute to particularly Ireland. They've had an outstanding 12 months, and deservedly won World Rugby's team of the year, coach of the year and player of the year."