* Intense encounter leads to red card for Du Plessis
* South Africa refuse to get drawn on impact of dismissal (Adds details)
By Greg Stutchbury
AUCKLAND, Sept 14 (Reuters) - Two tries from captain Kieran Read helped New Zealand grab the lead in the Rugby Championship on Saturday after a 29-15 victory over South Africa, who had Bismarck du Plessis sent off for two contentious yellow cards.
The bonus point victory came courtesy of tries from Read, Brodie Retallick and Sam Cane but at the cost of a collarbone injury to flyhalf Daniel Carter in a crunching tackle from hooker Du Plessis.
New Zealand coach Steve Hansen told reporters it appeared Carter had injured the AC joint in his right shoulder and that he could be out for between four and six weeks.
Du Plessis was sin-binned for the tackle then received a second yellow in the first minute of the second half for leading with his elbow into the throat of Liam Messam.
Neither Hansen nor his counterpart Heyneke Meyer were prepared to discuss the yellow cards in detail, with Read and Ma'a Nonu also sin-binned in the final 10 minutes, though Hansen said anyone leading with their elbow was at risk of a red card.
"In an intense battle like that, you're going to get moments and a referee has to make decisions in those moments," Hansen said.
"Perhaps Bismarck may have been unlucky on Dan's yellow card but he probably got the other ones right.
"I don't think it is legal to go putting your elbow in some one's throat," Hansen added tersely when asked about the two cards to du Plessis.
"The second card may well have been a red one rather than a yellow.
"But we have got no complaints. That's rugby and you just have to get on with it."
With both sides unbeaten in the tournament, the match had been billed as the most important in New Zealand since the 2011 World Cup final.
The Springboks had entered the game on a nine-match winning streak and were supremely confident after they had demolished Australia 38-12 last week. The All Blacks are also unbeaten in New Zealand since 2009 and at Eden Park since 1994.
The International Rugby Board's number one ranking was also on the line for the winners of the match and neither side disappointed in an intense encounter.
The collision zone was brutal with several players reeling away from the contact grabbing their heads, shoulders and ribs as they were hammered by their opponents.
The pivotal moment, however, occurred when Carter was crunched by Du Plessis in a tackle ruled by referee Romain Poite to be high, although television replays suggested the hooker had been hard done by.
The tackle sparked an all-in brawl, while the 47,362-sellout crowd bayed for the Springbok's blood as he trudged to the sideline.
The card left the combative Sharks player walking a thin line for the remainder of the game and although he had scored a first-half try when he returned, his reaction to a Messam tackle effectively ended the game as a contest.
Du Plessis braced himself for the tackle in the first minute of the second half, but led with his elbow which struck Messam in the throat and left the blindside flanker reeling away.
Poite referred the decision to television official George Ayoub who recommended a yellow card and the Frenchman had no choice but to show Du Plessis a second yellow then the red.
South Africa captain Jean de Villiers, however, said despite the dismissal of du Plessis, his side had not played well enough to win the game.
"The All Blacks are a tough team to play when you have 15 on the field so when you have 14 it's a tough ask," De Villiers said.
"It did take something of the spectacle away but that is what it is. They are a really good side.
"They were the better team on the day. They played better than us. We have to look at the way we performed because that was not a performance that was good enough to compete with them."
(Editing by Ed Osmond)