All Blacks lock Sam Whitelock is experiencing concussion symptoms and could miss the second Bledisloe Cup test against Australia at Eden Park, the team said on Wednesday.
The 32-year-old, the team's most experienced player with 118 caps, had suffered from headaches since the 16-16 first test with the Wallabies, assistant coach John Plumtree said.
"Sam had some headaches after the game," Plumtree told reporters in Auckland. "So we'll work through the concussion protocols and we'll see how he gets on this week.
"Hopefully he'll be all right for the weekend."
Tupou Vaa'i, who came off the bench for his debut last Sunday, is the likely replacement if Whitelock is ruled out, although Scott Barrett could be brought back following his recovery from foot surgery.
Plumtree added that utility back Beauden Barrett, who missed the first test at Wellington Regional Stadium with an Achilles' injury, played only had a small part in training on Wednesday.
Josh Ioane has been called into the side as cover in case Barrett or Richie Mo'unga, who had shoulder soreness after a succession of what coach Ian Foster deemed late tackles in the first game, are unable to play in Auckland on Sunday.
Plumtree, however, was optimistic they would both be available for selection.
"It looked like he (Barrett) was running pretty well," Plumtree said. "He's looking likely, absolutely, but he was looking likely this time last week as well.
"Richie had a little bit of a stinger in the shoulder but nothing too much."
Foster, who succeeded Steve Hansen after last year's Rugby World Cup, came under scrutiny after the All Blacks were outplayed by the Wallabies for much of the first game.
The All Blacks have held the Bledisloe Cup since 2003.
(Reporting by Greg Stutchbury; Editing by Peter Rutherford)
