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Whitelock, who started at lock in the All Blacks' 16-all draw over the weekend, suffered a head knock and is undergoing concussion protocols.
If Whitelock isn't cleared to play, it could mean a potential start for 20-year-old Tupou Vaa'i, who made his All Blacks debut off the bench last Sunday.
Scott Barrett could be back to help the All Blacks' lock stocks – but a lack of match fitness could see him play for Taranaki before joining the national side.
Meanwhile, Highlanders first-five Josh Ioane could be called into the team and trained with the squad in Auckland on Wednesday, with Beauden Barrett – who trained separately from the team – still seemingly recovering from an Achilles tendon injury that kept him out of the Bledisloe opener.
Richie Mo'unga, who coach Ian Foster admitted was sore after the first test, isn't a doubt for the second clash.
All Blacks selector Grant Fox said on Sky Sport's The Breakdown that they were assessing "a couple of injuries".
Foster is due to name the team on Friday at 11.30am.