However, the Warriors doctor was now awake and recovering well, his wife said.
"I know that people are quite concerned, but he looks good and he's doing well," she said.
She added: "He looks good, he's chatting and he's got a good sense of humour. He'll be in there for a bit longer, but he's looking good."
While he was making progress, he was not yet ready to talk to media himself, Mrs Mayhew said.
Dr Mayhew was on the sidelines for 131 All Blacks tests, and has been the team doctor for the Warriors for most of the past decade. He was appointed an Officer of the New Zealand Order of Merit for his services to sports medicine in the New Year's Honours list.
He was close to the late All Blacks star Jonah Lomu, and acted as a pallbearer at Lomu's Eden Park memorial service, following his death, aged 40, last November.