TJ Perenara's loss is Piri Weepu's gain.



In an ironic twist, Weepu is the surprise inclusion in the All Blacks' 28-man squad to tour Argentina and South Africa - a selection that also includes Richie McCaw.



The veteran halfback has been extended a lifeline after Hurricanes halfback Perenara succumbed to a stress fracture in his leg. It will sideline him for at least six weeks.



The injury reverses the circumstances that elevated Perenara above his former Wellington mentor in the initial Rugby Championship squad. It is a cruel blow for the 21-year-old, who is yet to make his test debut and now faces a race against time to recover for the end of year tour.



"TJ has suffered a stress fracture in his lower left leg and is expected to be out of rugby for at least six weeks and therefore will miss the rest of the Rugby Championship," All Blacks coach Steve Hansen said. "It's obviously a huge disappointment for him and us because, even though he hasn't had any game time yet for the All Blacks, he has been developing well within the squad."



Weepu was dropped after an average performance in the third test against France in New Plymouth in June. He was told to go away and improve his fitness and speed.



Hansen is satisfied the 30-year-old made those adjustments after turning out for the Auckland NPC side. His 71 tests of experience could be valuable in the absence of Dan Carter.



Counties Manukau and Chiefs halfback Augustine Pulu is understood to be next in line, but this trip was deemed too testing for a rookie. Pulu is also due to have surgery on his leg later in the year.



"We have selected Piri as a replacement for two reasons. One, given the environments we are going into, it would be unfair to bring in a novice halfback; and secondly, we have also seen advances in his game in the areas we asked him to improve in," Hansen said.



As expected, after a solid test debut in Wellington against Australia, Canterbury's Tom Taylor has been called in as cover for Carter, and McCaw's progress from a medial ligament knee injury suffered against Argentina will be monitored on tour.



"With Richie, we believe that the best chance of having him available to play against South Africa [in Johannesburg] is by having him travel with the squad and getting hands-on treatment from the All Blacks medical staff," Hansen added.



A decision on whether or not McCaw is available to play against South Africa will be made later in the week in Argentina. If he's not available, Canterbury's Matt Todd will join the squad in South Africa.



All Blacks squad: Forwards: Hookers: Dane Coles, Andrew Hore and Keven Mealamu. Props: Wyatt Crockett, Charlie Faumuina, Ben Franks, Owen Franks and Tony Woodcock. Locks: Brodie Retallick, Jeremy Thrush and Sam Whitelock. Loose forwards: Sam Cane, Steven Luatua, Richie McCaw, Liam Messam and Kieran Read. Backs: Halfbacks: Tawera Kerr-Barlow, Aaron Smith and Piri Weepu. First five-eighths: Beauden Barrett, Aaron Cruden and Tom Taylor. Midfielders: Ma'a Nonu and Conrad Smith. Outside backs: Israel Dagg, Charles Piutau, Julian Savea and Ben Smith.