The All Blacks need to work on their discipline according to Steve Hansen after two yellow cards in their opening win over Argentina.
Richie McCaw and Conrad Smith picked up 'dumb' yellow cards in the words of the Kiwi coach, and for a while it looked like it could prove costly, with Argentina leading with just under an hour played.
However the All Blacks stepped it up when they had to, and ran in two tries from Aaron Smith and Sam Cane, to secure the 26-16 win against their toughest pool opponents and put themselves on course for the last eight.
The fact that they were reduced to 13 men late in the first half was a concern though, McCaw binned for a stupid trip, followed by Smith cynically killing the ball as Argentina attacked.
And while it didn't cost them on this occasion, Hansen knows that they can't afford to repeat the trick, especially when the knock-out stages get underway.
"It was very, very hard. It took a long time to get on top and the fact we gave away two yellow cards, which were both warranted, meant we played for 20 minutes with only 14 players," said Hansen.
"That makes it tougher but in saying that, we're very happy with our guys, they showed a lot of fortitude.
"The two yellow cards today were pretty dumb. I've spoken to the guys, Conrad and Richie, they know they were dumb ones. Sometimes in the heat of the moment you have a brain explosion.
"The rest of the discipline was pretty good but we'll have a chat about it. We can't afford to keep playing with only 14 players on the track and at one point 13."
It was only the third yellow card of McCaw's career, but easily the most needless as he tripped Juan Martin Fernandez Lobbe when he was trying to take a quick tap penalty.
McCaw was booed by the crowd as he left the field, and the same happened on the final whistle, but the All Black captain admitted he deserved what he got for the infringement.
"It's one of those things, as soon as it happens you wish you hadn't," added McCaw.
"I knew straightaway, it was a reflex thing, not the right thing to do. I suffered the consequences and put the team under pressure."