SANZAAR is investigating why Sonny Bill Williams wasn't checked for concussion after the All Blacks midfielder looked dazed after suffering heavy contact in the second minute of the opening Bledisloe Cup match against the Wallabies in Sydney.
Footage has emerged of Williams struggling to get to his feet having attempted to bring down Wallabies skipper Michael Hopper in the 54-34 win.
Soon after the 32-year-old made two more tackles -- the latter saw teammate Brodie Retallick and Australian lock Adam Coleman land on top of his head.
Williams then retreated behind the goal posts after Wayne Barnes awarded the Wallabies a penalty, where he received no medical attention.
The cross-code star went on to play the rest of the match.
A SANZAAR spokesman confirmed to News Corp Australia they were looking into the matter after footage of the incident began to circulate on social media.
All Blacks assistant coach Ian Foster said that Williams had not been pushed at training in Dunedin on Tuesday ahead of the reverse fixture this weekend.
"Sonny took a knock in the weekend but he was symptom-free," Foster told reporters.
"The Doc has done what he always does when there is a suspicion of something. He was held back a little bit today so we could make sure he was absolutely clear but the signs are really positive."
When asked about the collision on Sunday, All Blacks coach Steve Hansen said no one had noticed any adverse effects.
"I think everyone missed it to be fair, otherwise the HIA doc would have taken him off," Hansen said.
"Our doc certainly would have taken him off."
The All Blacks will name their team for Bledisloe II on Thursday.