New Zealand's victory over the Pumas in Hamilton on Saturday saw Richie McCaw being ruled out for a month.
The hosts ran out 28-13 victors in an encounter that was rather spoilt by persistent rain. The worry for New Zealand, as they prepare to entertain the Springboks next week, is that a change of captain is required for the Rugby Championship run-in.
The diagnosis is that McCaw has suffered a medial ligament knee injury. Head coach Steve Hansen confirmed the seriousness of the injury.
"At this stage it looks like a four to five-weeker," he told stuff.co.nz.
"He might wake up in the morning and feel a lot better, but we're not thinking it's going to be like that. We might as well get it out now and get on with it."