McCaw out for up to five weeks All Blacks skipper Richie McCaw is set to miss the rest of the Rugby Championship after suffering a knee injury in the 28-13 defeat of Argentina in Hamilton. McCaw limped off in the 60th minute of his 119th Test on Saturday night and coach Steven Hansen says the flanker has medial ligament damage. "At this stage the Doc thinks it looks like a four to five-weeker," Hansen said. It's like all injuries. We won't know. He might wake up in the morning and feel a lot better, but I'm not thinking it's going to be like that. McCaw's injury happened after he made a tackle and his left leg was caught in the ensuing break-down. The All Blacks face South Africa in Auckland next weekend, before completing the tournament with matches away to the Pumas and the Springboks. New Zealand ended up scoring three tries - two to half-back Aaron Smith - to the Pumas' one in difficult, wet conditions to make it three wins from three rounds. Rain arrived early in the first half and stayed, leading to numerous handling errors by both sides. Argentina showed plenty of spirit, their first scrum a statement of intent with a big shove. But they were hurt by hooker Eusebio Guinazu's first-half sin-binning for breakdown infringements and by lineout problems that resulted in them losing a number of their throws. All Blacks No.8 Kieran Read produced another high work-rate performance, and he had a direct hand in two of his side's tries. Hansen said victory was the big positive from the night and he praised his players for exerting their own physicality on the game. "I thought the forwards played really good," he said. It wasn't a night for the backs, it was really difficult ... but I think there's enough positives there to look forward to next week. Argentina struck first with a try to No.8 Juan Manuel Leguizamon from a mistake in the fifth minute and coach Santiago Phelan said his team had gone into the game believing they could pull off an upset. But he said each error made against opposition of the quality of the All Blacks was expensive. "Overall we were competitive in every aspect of the game," he said. They were more clinical than us and that's something we need to keep improving. The All Blacks replied with a Dan Carter penalty, a goal that made him the first player to pass 1400 Test points. New Zealand then made used of Guinazu's absence to run in Aaron Smith's two tries, the first set up by an outrageous Read offload. The second came after a huge break from deep by Carter, back from a calf injury for just his second Test of the year. The All Blacks' third try began with a Read charge-down and ended with winger Julian Savea scoring his 14th touch-down in his 14th Test.