In May, Johnston was the figurehead for a tug of war between European clubs and the Pacific Island nations.
London Irish's Manu Samoa forward Daniel Leo told the Guardian newspaper that Johnston, who then recently signed a new two-year contract on the condition he did not feature in the World Cup starting in September.
Damian Hopley, chief executive of the Rugby Players' Association, told the newspaper: "It's a huge injustice that we can't see the best players representing their countries at the World Cup. World Cups are all about seeing the best play against the best. If you've got players being incentivised to retire from international rugby it goes against the grain of what a World Cup should be about."
The All Blacks might be in a state of flux due to Saturday's Super Rugby final taking out 17 players, but the feeling in Apia is that they remain a formidable outfit.
Johnston will help shore up one side of a scrum which is likely to come under severe pressure from the men in black.
Coach Steven Hansen has said he wants to keep things simple which is likely to represent a structured game, based around scrum, lineout, and quick ball.
Asked how preparations were going for next Wednesday's test at Apia Park, Betham said: "So far, so good. We've had a week and a half now with all the boys here in Samoa. We've had good sessions in the sun, but the good thing about it is we haven't had any major injuries to the players we have now. They're all tracking well and it's all about combinations now and how we front up to the All Blacks on the day."