The ongoing concussion-related injury of star fullback Leon MacDonald is New Zealand coach Graham Henry's biggest concern as he starts plotting his team's final assault on the Tri-Nations.

Following their emphatic 39-10 demolition over Australia at the weekend, to throw the Tri-Nations series wide open, the All Blacks go into the second half of the tournament with away matches to the Springboks (at Newlands on August 16) and the Wallabies (in Brisbane on September 13).

Although the Kiwis top the Tri-Nations standings, they will need to win at least one — probably both — of their away games to clinch the series — as the Boks already have an away win and the Aussies (with two wins from three starts) are also still in a very tight race.

But injuries, as often is the case, can threaten to derail any team, including New Zealand.

It was confirmed on Sunday that MacDonald and wing Rudi Wulf are the only injury concerns for the All Blacks as they prepare to leave for Cape Town on Friday.

MacDonald was forced to withdraw from the All Blacks starting 15 because of the ongoing effects of a head knock he suffered against South Africa almost a month ago.

Wulf strained his knee while playing for North Harbour in the Air New Zealand Cup at the weekend.

All Blacks' assistant coach Steve Hansen confirmed that MacDonald is doubtful for the trip to South Africa.

Hansen says MacDonald has been with his family since withdrawing from the squad and they have not spoken to him during that time.

The All Black coaching staff will make a decision later this week on whether MacDonald will travel with the squad to South Africa.

The New Zealand team doctor Deb Robinson will assess MacDonald in Christchurch this week.

"We certainly won't be rushing [MacDonald] back to play till he is ready," Hansen told the media on Sunday.

"We sent him home to be with his family and it's like any head injury it will come right eventually.

"He wasn't that far away but the Doc will see him during the week and we'll make assessments. If he's not right he won't be part of it."

New Zealand can only take 26 players to South Africa and Hansen confirmed on Sunday Piri Weepu would travel as the third scrumhalf, but that they had decided against taking an extra hooker — with props Tony Woodcock and John Afoa to cover the position should either Andrew Hore or Keven Mealamu get injured.

"We will use Tony Woodcock as the thrower [in the line-outs] and John Afoa as [the hooker] in the scrum," Hansen explained.

"Tony's a very good thrower and has been doing a bit of work on it quietly in the background.

"With all the injuries we've got in the hooking area we just think that's the best option."

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