New Zealand head coach Steve Hansen labelled his captain Richie McCaw “dumb” for the “brain explosion” which led to his sin-binning at Wembley.

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The Pumas led 13-12 at half-time after McCaw and experienced centre Conrad Smith were shown yellow cards. But a final-quarter surge, with tries from Aaron Smith and Sam Cane, plus 16 points from the boot of Dan Carter earned the “rusty” 2011 world champions an opening Pool C win.

“The two yellow cards today were pretty dumb. Rich and Conrad know they were dumb ones and sometimes in the heat of the moment you have a wee brain explosion,” said Hansen, who described both sin-binnings as “warranted”.

McCaw saw yellow for tripping Juan Martin Fernandez Lobbe as his opposite number took a quick tap penalty in front of referee Wayne Barnes’ nose.

The flanker said: “(It was) one of those things that as soon as that happens you wish you hadn’t. I knew straightaway.

“It was a reflex thing. It wasn’t the right thing to do. I suffered because of it and put the team under pressure which wasn’t the right thing to do.”

McCaw was booed in the sin-bin and at the end of the match. He added: “It’s happened before and if you get wound up about it, it’s not going to help you. You’ve got to block that kind of thing out. I was sitting in the sin-bin at the time, so I didn’t have a lot of comeback.”

Hansen believed the booing was a mark of respect for an All Black great. “You don’t get booed unless you’re any good. If you’re no good nobody cares,” Hansen said.

New Zealand trailed 16-12 early in the second half and seized control in the final quarter after Hansen turned to his replacements’ bench, with Sonny Bill Williams influential.

Wing Nehe Milner-Skudder somehow fumbled a Williams pass with the try-line in front of him before Aaron Smith darted over, enabling the All Blacks to seize control of the contest.

“The scoreboard would reflect it was very, very hard. It took a long time to get on top,” Hansen said. “There’s no doubt we were rusty, really rusty. Not only were we rusty, there’s a lot of apprehension in most of the teams.

“Everyone’s been half a second off the pace. That’s what comes with the World Cup, especially first round.” Argentina head coach

Daniel Hourcade admitted his side could not escape the All Blacks’ clutches in the second half after a first in which Guido Petti’s try was the difference.

“We were dominating and we had to stay that way, but it got to a point where they reacted, they took the ball and they never gave it up,” Hourcade said.

“When we were retrieving the ball we should’ve been able to have greater possession and been more effective. They were in constant attack and that made things difficult.”