The shake-up comes after the Springboks were beaten by Wales, New Zealand and Australia in recent weeks. Van der Westhuizen, 28, will now skipper the team in their Tri-Nations games against New Zealand in Pretoria on 7 August and against Australia in Cape Town on 14 August. He will also lead them in their defence of their World Cup in October.
Mallett said Teichmann could not be retained as captain as he was no longer a first-choice selection at No 8. Bobby Skinstad is preferred in that position. "To be captain, first of all your position in the starting 15 must be assured," Mallett said. "Looking at our best possible loose- forward combination for the World Cup, the selectors and I believe Gary is not assured of his place."
Van der Westhuizen, Springbok vice-captain in 1998, becomes the fourth captain used by Mallett this season, after Teichmann, Corne Krige and Johan Erasmus. Mallett has spoken to senior players to explain the decision. He said: "I was very aware that, because the players respected Teichmann, I would have a job on my hands getting the side behind the new captain."
Teichmann's place has gone to 22-year-old Bobby Skinstad, who returns from injury to take his place in the squad. "I don't think Gary's very happy at the moment." said Mallett. "He is upset about it. It's been a dream of his to go to this World Cup and it's a decision I have not enjoyed making."
Mallett recalled three veterans to the squad - World Cup-winning forwards Chris Rossouw and Ruben Kruger and the centre Brendan Venter, who made the last of his 14 Test appearances three years ago.
Craig Dowd has returned after injury to the All Blacks squad in time for the Pretoria match. Dowd was one of four additions named yesterday to the regular side for the 26-member squad for South Africa.
The New Zealand selectors have also given Gordon Slater a chance to revive his All Blacks career, recalled Carlos Spencer and for the first time included Canterbury's Reuben Thorne. The centre Pita Alatini, released from the squad to play for New Zealand A on Sunday, will also make the trip.
The most significant selections are those of Dowd, who has been out of action with a broken ankle and then a back injury, and that of Slater. Both will battle for the injured Carl Hoeft's spot in the front row.
New Zealand's coach, John Hart, said the additions to the squad were made specifically for the South African match with an eye as well on the World Cup. "It's a bit of both, but ideally it's what we need to cover in South Africa," Hart said.
South Africa squad (v New Zealand, at Pretoria, 7 Aug): G du Toit, R Fleck, H Honiball, D Kayser, P Montgomery, B Paulse, P Rossouw, A Snyman, W Swanepoel, S Terblanche, J van der Westhuizen (capt), Brendan Venter, S Boome, N Drotske, O du Randt, R Erasmus, A Garvey, R Kruger, O le Roux, K Otto, C Rossouw, B Skinstad, A van den Berg, A Bventer, C Visagie, A Vos.
New Zealand squad: P Alatini, T Brown, C Cullen, D Gibson, B Kelleher, J Lomu, J Marshall, A Mehrtens, C Spencer, T Umaga, J Wilson, A Blowers, R Brooke, C Dowd, G Feek, M Hammett, J Kronfeld, N Maxwell, K Meeuws, D Mika, A Oliver, T Randell (capt), G Slater, R Thorne, R Willis.
Arwel Thomas, who failed to earn a place in the Wales World Cup squad, will captain Swansea on their return to the Welsh League Premier Division next season. The outside-half has been appointed until Scott Gibbs returns from World Cup duty in October or November.