Fly-half Carlos Spencer kicked New Zealand to their fifth Tri-Nations crown in eight years as the All Blacks overcame a vastly-improved South Africa 19-11.

Spencer proved the difference in a hard-fought battle at Carisbrook, slotting four vital penalties while his South African opposite number Louis Koen had an off-day with the boot.

Koen missed two penalties as well as three drop-goal attempts as South Africa struggled to capitalise on an immense forward effort, with their back-row forwards led by skipper Corne Krige outstanding.

The All Blacks, who had humiliated South Africa 52-16 in Pretoria last month, were made to work far harder this time as they secured the Tri-Nations ahead of next Saturday's Bledisloe Cup decider with Australia in Auckland.

The Springboks failed to win a bonus point consigning them to the Tri-Nations wooden spoon, with Australia the runners-up.

All Blacks skipper Reuben Thorne paid tribute to the flawless display of Spencer, whose goalkicking had come under scrutiny earlier in the season after a defeat to England in June.

"He kicked really well. We've always believed in him and tonight just showed what he's capable of," said Thorne, adding he had not been surprised by a sharp improvement in South Africa's play.

"We expected them to come out fired up. They've had two disappointing losses and we knew they'd be really tough tonight and they were. Their defence was superb," said Thorne, who is now focused on wresting the Bledisloe Cup from Australian hands.

"We're looking forward to next week. Hopefully we can get the result we need," he said.

Krige was disappointed at the defeat - but admitted the performance would enable the Springboks to approach October's World Cup in a positive frame of mind.

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