LONDON • All Blacks skipper Richie McCaw pleaded guilty to a "dumb" moment which saw him sin-binned as the world champions struggled to beat Argentina in their World Cup opener on Sunday.

McCaw, the most capped player in Test rugby, got a yellow card for tripping Argentina's Juan Martin Fernandez Lobbe half an hour into the game.

The Pumas took advantage of his 10-minute exile, and later that of Conrad Smith, to stamp their authority on the Pool C game.

"It was dumb," McCaw said of the incident. "It was a reflex thing.

"It wasn't the right thing to do and we suffered because of it and put the team under pressure, which you can't afford to do."

The sentiment was shared by New Zealand coach Steve Hansen, who said: "The two yellow cards were pretty dumb. Sometimes, in the heat of the moment, you have a wee brain explosion."

Hansen backed referee Wayne Barnes in showing the yellow cards.

New Zealand were for a few minutes down to 13 men when Smith was ordered off too.

However, the world champions eventually won 26-16 in the Wembley encounter before a record 89,000 crowd.

From the spectators' view, New Zealand had some anxious moments. While they were short-handed, Argentina moved to a 16-12 lead, threatening an upset victory only a day after Japan had humiliated South Africa.

Some spectators booed the New Zealand skipper. But McCaw said he had not been worried about the scoreboard and insisted there was no panic in the ranks.

The All Blacks believed they would get on top of the Argentina pack and then the game would turn.

"So we had to change things but we had to make sure we didn't get all tense and worried about what might happen at the end," McCaw said. "We just wanted to focus on getting that sorted and I thought, for the most part of that second half, we started to win those contact areas.

"And when you start to do that, you focus on what's happening now rather than the scoreboard."

Hansen said the close encounter had been good for his side who were coming out of a month's break since their last game.

"There's no doubt we were rusty. There was a lot of apprehension with every team that's played.

"I have watched most of the games over the weekend and everyone's been probably half a step off the pace and that's what comes with the World Cup, especially the first round."

Hansen paid tribute to scrum-half Aaron Smith who re-ignited the All Blacks' attack with a well-taken try in the second half.

His speed was a problem for Argentina throughout the game.

"He's probably one of the best scrum-halves in the world. He scored a very timely try today."

Sam Cane also scored for the All Blacks with Dan Carter landing two conversions and four penalties.

New Zealand next take on Namibia on Thursday which should be an easier ride.

For Argentina, Guido Petti scored a try with Nicolas Sanchez kicking a conversion and three penalties.

Argentina coach Daniel Hourcade was disappointed that his side could not maintain their lead over the All Blacks.

"We were dominating and we had to stay that way but it got to the point where they reacted.

"They took the ball and never gave it up," he said.

AGENCE FRANCE-PRESSE