"The whole of our rugby league community is in shock," he said.
"Things are quite distraught at the moment. Her dad went [died] a couple of weeks ago."
Police had been called to the park on Saturday where the player collapsed to assist ambulance due to there being many bystanders.
"During the game she had the ball and she took a tackle. She got up and played the ball but she was unsteady on her feet", Mr Tamati said.
She had seemed fine immediately after the tackle and it did not appear as though she had received a knock to her head, he said.
"The ref didn't see the knock but saw the tackle...we didn't think it was a head injury for the type of tackle that happened."
The coach and other staff saw that Waikato was unsteady on her feet as she played the ball and called for her to come off.
She was being helped to the sideline and went to go to her partner when she fainted, he said.
"She had taken a knock, she had a cut to her eye...Nobody anticipated what was going to happen as she came to the sideline."
New Zealand Rugby League concussion and head injury policy states that a player who cannot answer any question on a sideline concussion checklist in conjunction with any signs of acute concussion must stop playing and be removed from the field.
"There has long been a perception that a concussion occurs only when there is a loss of consciousness," the policy said.
"This perception is incorrect as concussions can occur without loss of consciousness and range in severity from brief periods of confusion through to a significant loss of consciousness."
Tamati said Rugby League Hawke's Bay had imposed extra rules so a referee that saw any type of head injury had to stop the game and the remove the player from the field.
This did not happen on Saturday because the referee did not think the player had received a knock to her head during the tackle and something like this could be missed, he said.
"Our refs are quite sensitive of tackles, in particular high tackles, we're mindful of this, so are our players but these accidents do happen."
Everyone at Rugby League Hawke's Bay was thinking of Waikato and her family at such a hard time, he said.
"I know she has a young family, it's hard for us, especially when families are concerned.
"We're mindful that they are going through a difficult time, all of our love and best wishes go out to them."
