Carter was always eyeing the exit door following the World Cup and his deal with French club Racing Metro is set to make him the highest-paid rugby player ever.
The Crusaders were this week left resigned to losing another No10 when Colin Slade announced he had also opted for France, signing a three-year contract with Pau.
Which leaves Barrett and Cruden, locked into New Zealand Rugby through 2016 and 2017, respectively. But Barrett may have other engagements next year, at least for the early part of the international calendar.
The Hurricanes pivot yesterday expressed his interest in playing sevens next season, with the lure of Olympic gold turning the 23-year-old's head.
If Barrett is eventually included in Gordon Tietjens' squad, he would miss the All Blacks' June series with Wales, along with the opening stages of the Rugby Championship.
Which would leave Cruden, having already turned down an approach by Tietjens, the unequivocal first choice when Steve Hansen names his first post-World Cup team.
It's questionable whether New Zealand Rugby would sanction Barrett's dalliance with sevens, given the shortfall it would create in a key position. And it's also questionable whether Barrett would be wise pursuing such an option, having waited so patiently for a shot in the All Blacks' No10 jersey.
Because if Barrett does head to Rio, Cruden, still 26, will receive a consistent run in that jersey and, with it, the chance to secure the role as Carter's successor ahead of the 2017 Lions tour.
For now, though, Cruden is focused on once again testing himself against the best, albeit with Carter sliding a space further along the Crusaders' backline.
"Those are the sorts of challenges you look forward to as a player," Cruden said of the clash with Carter. "He's been the marquee No10 in world rugby for a number of years now and it's good to test yourself as an individual to see where you're at."
The outcome of that examination will be one of several factors that determine the first-choice first five in England. Goal-kicking will be another, and it's aspect for which Cruden has copped some criticism this year.
His 73 per cent success rate this season sits behind Carter (81 per cent), though Cruden has taken almost twice as many attempts. And that rate is also ahead of Slade (69 per cent) and Barrett (68 per cent), leaving Cruden content with his form from the kicking tee.
"The media make a fuss about a lot of things," he said. "But, for me, it was always about just worrying about what I can control and my processes during the week. It's starting to come along now.
"Rugby is a lot more than just about goal-kicking. As a No10, you want to focus on certain areas of your game. Being a driver and a leader of the team is a major focus for me aswell."
He could soon be leading the All Blacks on a long-term basis.
