It hasn't happened often during his decade in Irish rugby, but on Saturday Joe Schmidt was thoroughly out-coached by the Japanese brains trust.
It is hard to escape the idea that the coach of the year in 2018 has been figured out by his rivals in the following calendar year. Shizuoka will go down as the worst defeat of his tenure, unless of course there are more disasters to come in Japan .
At the worst possible time, the magic has worn off.
On the evidence of the team's performance, the coach got the preparation, team selection and game-plan wrong.
His leaders let him down in the trenches with Rory Best's lineout failings and accuracy with the ball deserting him and Peter O'Mahony losing his cool in an ill-disciplined display. Johnny Sexton was badly missed.
For some reason, Schmidt chose to criticise the match referee two days before the game against the tournament hosts. Whatever complaints he had about Angus Gardner, he'd have been wiser to keep his counsel.
They can't blame the referee, even if the Australian official gave a couple of marginal calls Japan's way.
Ireland should be good enough to play the referee and do enough themselves to take him out of the equation. Especially when they're in complete control on the scoreboard.
In the Fukuroi furnace, it never felt like that advantage translated into on-field dominance as the hosts routinely stretched their guests and made life deeply uncomfortable.
It was a world away from the opening weekend supremacy over Scotland when Best did an 80-minute shift for some reason and Ireland looked a million dollars.
Four years ago, Schmidt and his team put all of their energy into beating France and a week later had nothing left in the tank for their quarter-final against Argentina who beat them playing a high-speed, ultra-intense game-plan.
On Saturday, it was like watching a re-run only this time the blow isn't fatal.
Ireland should still get to the last eight and, if results go their way, may yet top the pool. Two bonus-point wins over Russia and Samoa will be enough to secure their place.
The coach gets plenty of credit on the great days, but he must also accept his share of the blame for a defeat that will go down as one of the greatest World Cup upsets.
Yesterday's review session would have centred around the players' roles in the defeat, the individual and systems errors that allowed Japan into the game but the New Zealander must look closer to home for answers.
The fear is that he has run out of time and that there isn't enough training sessions between now and the quarter-final to fix the myriad of issues exposed by Jamie Joseph and Tony Brown, the Japan brains trust.
And in the flood of reaction to the defeat, the quality of the Brave Blossoms' performance shouldn't be lost. The hosts gave their greatest performance to beat this Ireland team.
Schmidt tried to warn us, but if you big up every opponent ahead of every day nobody will hear you when you actually cry wolf.
The mitigating circumstances exist. It was incredibly humid, Japan had an extra two days to prepare and had invested far more time in Ireland than they had in Russia on opening night. They were backed by a wall of noise and the electricity from the crowd fed into a turbo-charged performance.
But for all of that, Ireland should have won the match from the commanding position they held at the end of the first-quarter.
The pillars of their game let them down. Their discipline was poor, their set-piece melted and their senior men wilted in the heat.
Whether they weren't getting the messages from above or simply ignored them, Ireland allowed their opponents dictate the terms of engagement and got drawn into a helter-skelter game that suited the well-drilled hosts down to the ground.
Even in a winning position, they made panicked decisions and paid the price.
What was most galling about the way Japan played was that their style of rugby is exactly the kind that Schmidt insists can't be played at this level due to a lack of preparation time.
Their skill levels were higher than the higher-profile Irish players, their passing slicker and the pace relentless.
Nobody saw the result coming, not even those of us who thought Japan were a better team than they were being given credit for.
The bookies were rating them as 21-point outsiders, the locals were hoping to get within two tries of Schmidt's side.
Their coaching team and players thought differently and delighted in turning the tables on tier one opponents once again.
Before Ireland's crushing defeat to England, Joseph and Brown spent time in Eddie Jones' camp watching how the Australian put together a game-plan that negated Ireland's strengths.
They took what was applicable to their own team and implemented it brilliantly. There is a template there for New Zealand or South Africa to work off, presuming Ireland don't slip up again.
And they shouldn't. Just as the Scotland team didn't make them the best team in the world, Saturday's loss didn't make them the worst.
After Twickenham, Schmidt fronted house and the players worked their way back to form behind closed doors.
They have little time to do so this week, but Russia and Samoa are eminently winnable games.
Four years ago, South Africa lost to Japan and emerged from the crisis to reach the semi-final and run New Zealand closer than anyone.
That's the kind of history Ireland came to make and they'd take a similar reversal of fortunes now.
In the aftermath of that game in Brighton, Heyneke Meyer apologised to the South African nation.
We won't hold our breath for Schmidt to do likewise, but unless he learns from his own mistakes his team are doomed.
Rugby World Cup 2019
So, what happened? By now we've sifted through a lot of post-mortems and, while this is a new week, it's worth taking a closer look back at how this Irish team was so badly taken apart. Those who fail to learn from history are condemned to repeat it, and there are major lessons in this defeat.