The All Blacks, who had never won in four previous matches against the Springboks in Port Elizabeth, were out of the blocks quickly with fullback Israel Dagg, playing his first test of the year after a thigh injury, breaking the defensive line in just the second minute.
He released Jimmy Cowan but the halfback was dragged down just short of the line by the flying Bryan Habana and then a misplaced pass from Sonny Bill Williams with the defence stretched ended the move.
A deft grubber from Slade, one of his few high points, caused more problems minutes later but after good work by Hosea Gear and Sonny Bill Williams, centre Kahui's pass was intercepted by his opposite Jaque Fourie to snuff out another potential tryscoring chance.
They were made to pay for their inability to take their chances by the recalled Steyn who slotted two penalties inside the opening 10 minutes to give the hosts a lead that belied their lack of possession.
He made it three from three to land another penalty from 50 metres, and bring up his 100th point against the All Blacks, and his opposite Slade missed a kickable chance of his own before a fourth Steyn penalty, followed by a drop goal, gave the hosts a 15-0 lead approaching halftime.
Desperate to get on the board before the break, the All Blacks then scored from a set piece with Kahui going over for his sixth test try after a lineout move. Sonny Bill Williams' inside ball put Gear through a hole and Kahui showed strength to hold off two tacklers to score an unconverted try.
The All Blacks had only themselves to blame for being behind at the interval after breaching the Springboks' defence on numerous times but lacking the patience to take full toll.
After another sizzling Dagg break after the resumption, Cowan was denied a try when South African television match official (TMO) Shaun Veldsman told Irish referee George Clancy that the pass from Dagg had gone forward. TMOs can only rule on action over the tryline but Dagg's pass had drifted forward in the field of play.
Steyn extended the lead with his fifth penalty after a dominant Springboks scrum before midway through the half Slade, who appeared to pick up a calf injury, was replaced by Piri Weepu. The Canterbury pivot may be in danger of losing the back-up role to Dan Carter at the World Cup especially after the superb provincial form of rival Aaron Cruden.
Tony Woodcock, returning to the All Blacks after a lengthy foot injury, threw a scare into the camp when he left the field, but it was a blow to the nose rather than a recurrence of the previous injury.
The All Blacks had few chances to score in the second half and when they did, Dagg and Isaia Toeava both lost the ball forward.
Despite the loss, the All Blacks selectors would have been happy with the showing of Dagg, Toeava, Kahui and Woodcock in their only chance to shine prior to the naming of the World Cup squad on Tuesday.
South Africa 18 (Morne Steyn 5 pen, drop goal) New Zealand 5 (Richard Kahui try). Halftime: 15-5.
- NZPA
