WEMBLEY, London -- The All Blacks got their Rugby World Cup campaign off to a winning start against a well-drilled Argentina side but New Zealand coach Steve Hansen was less than impressed with the two sin-binnings his team conceded in the first-half describing them as "dumb".

Approaching the final quarter of the first-half, captain Richie McCaw was sin-binned for a trip in the 29th minute and Conrad Smith was then dispatched with a yellow card seven minutes later for an infringement close to the All Blacks' line.

Hansen, though quick to praise his team and Argentina for a fantastic game, was decidedly unimpressed with his team's discipline when addressing the press post-match.

"The two yellow cards today were pretty dumb," Hansen said. "Rich and Conrad know they were dumb ones and sometimes in the heat of the moment you have a wee brain explosion." The All Blacks coach added both sin-bins were "warranted".

For McCaw, he cut the image post-match of someone who knew he had acted foolishly and was a touch sheepish when talking about what was the third yellow card in his lengthy Test career. He was sin-binned for tripping Juan Martin Fernandez Lobbe when the Pumas openside quick-tapped a penalty.

"[It was] one of those things that as soon as that happens you wish you hadn't. I knew straightaway," McCaw said. "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 when he was dispatched to the sin-bin and was later greeted with a similar welcome when interviewed on the field after the final whistle.

Hansen described it as a "mark of respect" adding: "You don't get booed unless you're any good. If you're no good nobody cares."

McCaw said of the volatile reaction: "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."

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