New Zealand Keven Mealamu is to undergo surgery on a ruptured chest muscle and will be out of rugby for at least four months.

The hooker left the field late in the All Blacks defeat to South Africa in Durban last weekend and had an MRI scan on his return to Auckland on Tuesday which confirmed a ruptured pectoralis major tendon on the left side of his chest.

"It's incredibly disappointing for Keven but he is in a positive frame of mind and will undergo surgery on Friday," All Blacks doctor Deb Robinson said.

The 30-year-old will miss the remainder of New Zealand's Tri-Nations campaign and the end of year tour.

Several of Mealamu's All Blacks team-mates will be in action this weekend though.

Luke McAlister has been named on the bench for North Harbour's game against Tasman on Friday, while Aled de Malmanche and Brendon Leonard (Waikato), Bryn Evans (Hawke's Bay), Cory Jane (Wellington), John Afoa (Auckland and Tanerau Latimer (Bay of Plenty) are all available for their provinces this weekend.

Those players, plus Kieran Read (Canterbury), Jason Eaton (Taranaki), Piri Weepu, Neemia Tialata and Rodney So'oialo (Wellington) will all be available for round three.

The All Blacks assemble again for a one-day training camp in Auckland on August 12 before heading to Sydney on August 16 to prepare for the Bledisloe Cup Test against Australia at ANZ Stadium on August 22.