It has been Stephen Kearney's main concern over the last few years, and on the evidence of the past week, continues to be the Kiwis' Achilles heel.
If the Kiwis are to retain the World Cup, maintaining an intensity of performance across the full 80 minutes is the crucial ingredient.
This team is definitely good enough to compete with - and beat - both England and Australia - but it will take a concentrated, focused effort of the kind that has been rare in the past few years.
"We have learned that we can't afford to switch off at any time," Kearney told the Herald on Sunday back in July. "The Australians always punish you, they always take advantage of any lapse."
The game against Samoa last Monday was disturbing not so much for the way the Kiwis eased off the throttle in the second half (it can happen) but more for their inability to wrest back control of the match, as they allowed the Pacific side to score four tries in 12 minutes. This wasn't the Kiwis' typical slow start to the tournament; in fact they began well before their second half fade.