All Blacks: Hansen unsure on Carter's diagnosis

All Blacks coach Steve Hansen kept his promise to alter his side for the third test against Ireland, but a couple of injuries have also forced his hand.

Hansen has made six changes for Saturday's night's final test in Hamilton, with Dan Carter and Kieran Reid among those sitting out the dead rubber.

Carter strained his right hamstring at training on Tuesday and should be on the sidelines for two to three weeks, while Read has been rested after failing concussion tests following a repeat head knock last weekend.

The pair's enforced absence sees Aaron Cruden coming into the side at first five-eighths and Richie McCaw starting at No 8 for the first time in his 105-test international career.

Carter's injury is particularly worrying for the Crusaders' Super 15 hopes, considering the pivot was kept out of action for six weeks after injuring his hamstring for the first time in the Crusaders' match at Twickenham last year.

Hansen was hopeful this strain was not as severe but admitted he was unsure over the exact diagnosis.

"He should be a couple of weeks or three weeks - we're not really sure," Hansen said. "It's not that bad but hamstrings are annoying things if you're ever fast enough to have one. They tend to hang around for a bit."

The Crusaders will also be worried about the status of Read who was forced off at halftime during the series-clinching 22-19 win in Christchurch.

"He'll be out until such time that he can pass all the concussion tests that say he's OK," Hansen said.

Hansen felt comfortable with Read's replacement on the back of the scrum, despite McCaw's relative inexperience in that position in the test arena.

"Richie's comfortable at [No] 8. He knows all the calls, he's been with us the last month - it just makes sense," he said. "It's just a means to an end. I've said before and I'll keep saying it, I think he's the best No 7 in the world, regardless of what other people are saying.

"But, unfortunately, [Read] is not here and the make-up of the loose forward trio means he has to shift to another position."

Sam Cane will make his first test start in McCaw's place, while Chiefs teammate Liam Messam gets the nod at blindside. Messam, who was only called into the squad as injury cover this week, was preferred to Adam Thompson, who Hansen thought needed a break.

"Liam Messam has come in to start the match, which has probably raised a few eyebrows, but Adam Thompson's played a lot of rugby and his body's been knocked around a fair bit, so we just felt that he could freshen up a wee bit."

That's also he case at lock where Luke Romano will make his debut in place of Brodie Retallick, as well as on the wing where Hosea Gear and Ben Smith come in for Zac Guildford and Julian Savea.

"Right from the word go, we felt that if this series had been wrapped up by Christchurch then we would look to make some strategic changes," Hansen said.

But that's not to say the All Blacks were under-estimating the Irish, nor the importance of their 107-year unbeaten run over the men in green, who name their side later today.

"We got a massive challenge last week from the Irish and we've got to step up to that challenge this week," Hansen said. "Ireland have given us a good tap on the chin and said, 'you better front up or we'll take that record off you'."

All Blacks team to play Ireland at Waikato Stadium in Hamilton on Saturday (7.35pm): Israel Dagg, Ben Smith, Conrad Smith, Sonny Bill Williams, Hosea Gear, Aaron Cruden, Aaron Smith, Richie McCaw (c), Sam Cane, Liam Messam, Sam Whitelock, Luke Romano, Owen Franks, Andrew Hore, Tony Woodcock. Reserves: Keven Mealamu, Ben Franks, Adam Thomson, Brodie Retallick, Piri Weepu, Beauden Barrett, Tamati Ellison.