The warnings have been frequent and underpinned many of the superb All Black performances in Steve Hansen's reign.
Any top team playing five per cent below their best is at risk against the other premier sides, he'd say. While there will be debate about the percentage drop in quality from the All Blacks, they struck that gruesome scenario at the worst time in Yokohama.
England played with wondrous venom and control throughout their World Cup semifinal as they dominated the tournament favourites and toppled their dreams of a third straight title.
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Where the All Blacks hit early and sustained the quarter-final heat on Ireland, a week later they were the unrecognisable victims.
As much as the All Blacks tried to slither and wriggle their way into clear air, they were hunted and bashed by a relentless England team who pressed forward with every attacking or defensive play.
It was a masterclass in belief and a tribute to the coaching and selection talents of Eddie Jones and his crew.
Before the match opinions about the outcome were divided along bloodlines. The All Blacks had the historical advantage but England were a team on the rise and it might come down to the kicking percentages of Richie Mo'unga and Owen Farrell.
Even that theory was wide of the mark as England unfurled a game for the occasion. They were half a step in front of the All Blacks all game and that difference produced a stunning 19-7 triumph - one which could have been so much more.
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Farrell gave the kicking tee to sureshot George Ford while Mo'unga only had one attempt after England messed up a defensive lineout. That was a rare blemish while mistakes littered the All Blacks' profile.
England's lineout purred with the majestic Maro Itoje and Courtney Lawes while the All Blacks spluttered with double the targets and had a scrum which wobbled as well.
The front five creaked for most of the match and that malaise infected the rest of the side. They started to infringe more and make unwise decisions because of the mounting pressure as England kept a chokehold.
When Aaron Smith tried a bomb from an attacking lineout near England's 22, things looked more askew and that was in the first quarter. England were energised and the All Blacks looked wan.
That malaise continued after the break as the accuracy in their game deteriorated. Passes went astray, kicks were inaccurate, tackles missed as anxiety took a stronger hold.
In midfield, Jack Goodhue and Anton Lienert-Brown gave it all but they had little to work with. The twin playmaker scheme got few chances to work with effective possession as Mo'unga was enveloped and Beauden Barrett was lassoed while it seemed like a triumph if the pack made it across the advantage line.
It was tough going and England feasted on that anxiety and shut down any signs of an All Black final quarter surge. They tried but it was high risk with no reward against England's marauders.
Jordie Barrett clocked Angus Ta'avao in the mush with an injudicious offload, Sam Whitelock had a penalty reversed after he pushed Farrell in the face, Brodie Retallick's offside in a maul drew a warning about a sin-bin for the next offender.
England were way too good and with the scent of victory would not let go. If they repeat this fine performance a second Webb Ellis Cup is realistic but holding that form will be their greatest challenge.