He was right to take his time to confirm his decision. A bit of him must have been tempted to think about carrying on. There wasn't anything about his mental or physical prowess at the World Cup that suggested last orders were imminent.
On the contrary. There were six world class loose forwards on show in the World Cup final and one stood out as being that little bit better. It was McCaw.
The rest of the world had a bit of a love-in with David Pocock and Michael Hooper during the tournament. Portrayed as the new king's of the tackled ball, they ended up looking a little Emperor's new clothes by the final whistle. McCaw not only snatched more tackled ball possession than they did, he contributed across a broader portfolio.
Pocock is the greatest one trick pony the game has known, but as Wallaby coach Michael Cheika watched the final play out, he knew that if McCaw had been in his team, the chances were good the outcome would have been different.
The final was another remarkable, near faultless performance by McCaw and yet it almost went without full recognition. When All Black coach Steve Hansen - who was involved in nearly all of McCaw's 148 tests - says he can't recall the skipper having a bad one, that's not nostalgic, rose-tinted remembering.
McCaw really didn't have a bad test and that made his excellence a little harder to detect towards the end of his career. It became almost taken for granted and instead, particularly at the World Cup, the accolades poured in for the likes of Daniel Carter, Jerome Kaino and Ben Smith.
The thing with the former two is that they were being lauded largely because they were returning to the sort of form they had won global recognition for earlier in their careers.
Those who drop and climb are easy to see and redemption is a theme that evokes stronger emotional responses.
McCaw was perhaps a victim of his consistency in that people stopped seeing the relentless excellence because it was the norm.
Watching him dominate in the final and maraud across Twickenham like some science-fiction cyborg, he looked like he could go on for ever. So what that his 35th birthday is on the horizon, McCaw posted fitness testing results in June that were not only miles ahead of his peers, they were ahead of his younger self.
If he'd fancied it, physically at least, he could have gone on for another year. He probably could have made it to take on the Lions in 2017 because as All Black strength and conditioning coach Nic Gill observed, the beauty of McCaw is that he never had any pace to lose.
His game was built on his endurance capacity and his unprecedented ability to end a game covering the ground at the same pace as when he started.
But mentally, he knows he doesn't have the same hunger he once had. He knows the fire inside him has been doused and without it, he couldn't ever be the same player. Why risk tainting a legacy that is the greatest rugby has known?
That's beyond dispute - McCaw is the greatest All Black in history. It's tragically poignant that the one man whose legacy could have matched his was taken this week.
It's an open-ended, subjective business trying to define greatness but if the qualities are confined to performance, longevity, character and influence, Jonah Lomu can match McCaw in three.
Fate denied Lomu the longevity component and arguably, it is McCaw's durability that in itself, makes him the greatest player of the age.
Players in his position don't typically last. The impacts he endured each test were equivalent to moderate car crashes and he managed 148. His body may punish him later in life, but he'll live with that, knowing that holding up the way it did, has given him currency for life.
Brand McCaw will no doubt soar in value now - becoming worth considerably more in retirement than it was when he was playing. He'll inherit the mythical title of patriarchal All Black from Sir Colin Meads and no doubt be on TV screens just as much as he ever was.
And he deserves everything. He has earned it all - literally in blood and sweat. But as much as material wealth is a welcome by-product of his endeavour, it won't mean much to him at all in comparison with the richness he has left behind in the All Blacks.
If he was driven by one overriding goal throughout his 15 years, it was to leave the All Black jersey in better shape than he found it. He can be certain he did that.
He can be certain that the All Blacks he leaves behind are infinitely more professional and rounded than they were when he arrived in 2001.
He has been the driving force of massive change. In 2004, All Blacks were being put in the recovery position by the Springboks, following an infamous court session that had got out hand.
Institutionalised drinking was condoned and accepted back then which was bad enough, but what it illustrated was a lack of desire to be the best. The All Blacks were talking rather than living professional lives back then. Relentless excellence - the sort McCaw has produced - has been underpinned by self-discipline, restraint and sacrifice. A whole generation of All Blacks have come under McCaw's spell and seen the rewards that await them if they take personal responsibility for all aspects of their lives.
That's his true legacy - how deeply ingrained and understood professionalism is now. The statistics he has racked up may in time be broken, but the culture he has helped create is highly likely to endure long after he's gone.
And for all that he achieved and gave to the jersey, maybe his greatest pleasure will be seeing Sam Cane fill it next year and do his level best to uphold all the values of the man from whom he inherited it.
