After the All Blacks produced a performance for the ages to narrowly knock Ireland out of the World Cup a year ago, they just needed the superior discipline and cohesion in a far more tepid affair at the Aviva Stadium.
"It's a funny old feeling because we don't tend to have it too much in that dressing room," Farrell told a news conference, describing the atmosphere as sombre after Ireland's first loss at home since 2021 and heaviest defeat in Dublin since 2019.
"I thought we prepped well but we didn't manage to put our game out on the field. There were too many errors and the energy and the accuracy wasn't what was needed to win a Test match like that."
Farrell, overseeing his last series before stepping away temporarily next year to lead the British & Irish Lions in Australia, said his side were particularly guilty of compounding their problems by piling error onto error, resulting in 13 penalty concessions.
"Points come on the back of that. We did that a number of times. We need to fix up our mentality as far as that's concerned. We became a little bit too desperate," he said.
"We move on, we have to. We have to find the solutions as soon as we possibly can because we have a hungry side in Argentina who have played some really good rugby at this period in time."
Ireland will next Friday face an Argentina side coming off the back of a solid Rugby Championship before closing their November series against Fiji and Australia.
