All Blacks v Springboks: Selection headaches for NZ after second-string smashing of Argentina

Facing South Africa for the 100th time looms as a tough challenge for the All Blacks, but coaches and selectors may face an even sterner test picking which 23 players will take the field at Townsville.

After the first four rounds of this year's Rugby Championship, the All Blacks are the only unbeaten side left in the competition, sealing back-to-back doubles over Australia and Argentina.

The second victory against Los Pumas - 36-13 at Brisbane last week - was achieved with an almost entirely rotated starting XV, with coach Ian Foster making 11 changes from the previous week.

But the form of the All Blacks second-stringers has only created more headaches for selectors, who now decide which players will miss out on the matchday 23.

"There's a lot of disappointed players who don't get selected," explains assistant coach John Plumtree.

Among the forwards, in particular, Ethan Blackcadder's form against Argentina must be weighed against equally impressive displays by Akira Ioane against Australia, as one of many selection dilemmas.

While many sporting sides around the world would face a challenge ensuring the unlucky players are kept happy, the All Blacks won't have such problems, insists Plumtree.

"The one thing that's probably different about this group [is] we're really tight and united," he says. "Everyone who does miss out just really wants to help the 23 prepare.

"While there'll be some internal disappointment that they're not in the 23, it's a really happy bunch at the moment. You don't see it in them.

"It's really good to see, and it's part of the culture and environment that Fozzie has created."

The All Blacks will name their team to face South Africa on Thursday.

Meanwhile, the All Blacks are braced for what they know will be a physical encounter with their great rivals, renowned for their forward-oriented style of play.

After living and playing in South Africa, Plumtree is well versed on the challenges the Springboks will bring.

And despite South Africa's recent woes - consecutive defeats to Australia - Plumtree says the All Blacks can't let the Springboks stymy their gameplan.

"In particular, this is going to be the toughest forward battle since I've been involved," he adds. "All the boys know that. 

"Everything we need to do has to have more power, more speed. We've got to play the game at a high tempo, because that's our game.

"We can't fall into the trap of the game slowing down or anything like that. We've got to make sure that we play our game and what that looks like."

Join us at 7pm Saturday for live updates of the All Blacks v South Africa Rugby Championship clash