Richie McCaw ruled out for a month

New Zealand captain Richie McCaw has been ruled out for at least four weeks with ligament damage.

The flanker was forced off during Saturday's 28-13 win over Argentina in the Rugby Championship.

"He's done a medial ligament and it looks like he could be out for four or five weeks," All Blacks coach Steve Hansen is quoted as saying by Sky Sports News.

McCaw recently returned to international rugby following a seven-month sabbatical from the sport.