Dan Carter weighs in on who should be Scott Robertson's All Black 10

Beauden Barrett's decision to return to New Zealand on a long-term deal after a year in Japan's League One threw a spanner in the All Blacks selection works, and while it's a great selection issue for coach Scott Robertson to have, the call will have to be made over which world-class first five-eighth misses out on the iconic No. 10 jersey.

The debate is largely between Barrett and Chiefs maestro Damian McKenzie, both of whom were key cogs for the All Blacks' 2023 Rugby World Cup campaign, although neither started at first five-eighth due to the form - and availability - of Richie Mo'unga.

Mo'unga's absence due to his long-term deal with Toshiba Brave Lupus in Japan making him ineligible for All Blacks selection is something that undoubtedly hurts Kiwi fans, and while Carter has the highest of praise for Mo'unga, he isn't sure a change in eligibility rules is the right call for New Zealand Rugby.

"I don't think it's just something you change immediately when, when you feel like there's a player that you'd love to have," Carter told Newshub when promoting his Beat Dan Carter initiative with Unicef.

"In my opinion, [Richie Mo'unga] is probably the best No. 10 in the world. As sad as it was to see him leave, he left for his reasons and to spend more time with his family.

"I'm sure he's enjoying his time in Japan and I'm sure there's a part of Razor that wouldn't mind having him back as well.

"The priority is making sure that New Zealand rugby is as strong as it possibly can be and if those eligibility rules change then who knows, we might see more players departing."

With Barrett and McKenzie leading a pack of aspiring playmakers in New Zealand, Robertson won't be left desperate for a reunion with his former Crusaders colleague.

Stephen Perofeta and Brett Cameron would appear to be the next best options as specialist 10s, both 27 years of age with an All Blacks debut under their belt.

Barrett's 123 caps in black sees the 32-year-old offer an experienced head to lead Robertson's attack, while McKenzie, at 29, has matured into a tactical threat while maintaining the mercurial running game that saw him earn an All Blacks debut in 2016 at fullback.

There's plenty to debate on behalf of both players and while Carter may be the best qualified to split those hairs, the All Black great stopped short of making a definitive selection.

"You've obviously got Beaudy coming back, a proven playmaker and everyone knows what he's capable of, so it's great to have him recommitted for a long period.

"And it's hard to go past Damian McKenzie and the impact that he has every time he plays for the Chiefs. It's awesome to see him in fine form.

"It's definitely a battle for those two boys."

The rugby icon's latest charitable endeavour sees Carter challenge the rugby community to beat him in a one-hour shoot-out, with the 42-year-old having achieved a benchmark of 273 successful attempts off the tee.

Proceeds will go to providing clean water for kids in the Pacific. The challenge comes two years after his last fundraising effort, a 24-hour kickathon, for the same cause.

"I was overwhelmed with the support that I got for the kickathon, two years ago.

"We've been working hard behind the scenes to try and think of another fundraising campaign. I'm not sure if in my old age that I can kick 24 hours again.

"I've set the challenge and empower people and teams to try and beat me and, and obviously pick up and fundraise along the way."