After he was hit by the ball he thought it had caused a migraine.
As the game progressed, he noticed that he was losing the ability to speak properly. He went to Rotorua hospital on the way home.
He went into surgery last Friday in Waikato Hospital to remove the build-up of blood and clear the area that was swelling.
It had originally been planned for Mr McKnight to go to ABI Rehabilitation in Auckland last Wednesday, but he had a visit from the doctors who had reviewed the scans and said surgery was needed.
"It came as a hell of a shock," he said, adding when he woke up he was "so relieved".
His speech was "miles better" and he will be referred to a local speech therapist to bring it back to 100 per cent.
Mr McKnight started playing cricket when he attended Kaitao Intermediate and really got into it in 1991 when he helped form the Geyser City Cricket Club.
The accident had been a massive learning curve. He bought a helmet a couple of years ago and wore it in a match early this season, but found it made it difficult to see the ball. "I think everyone should be wearing a helmet in terms of batting."
He was lucky and was looking to be involved in a campaign to raise awareness around the need for players to wear helmets.
"I don't mind talking to people about what I went through," he said, noting it was now a matter of taking it easy.
Mr McKnight said his employers, Red Stag Timber, had been good to him and that he was grateful for the support from friends, family and doctors at Waikato Hospital.
"I've got the chance to live my life again. It could have been so close in the end," he said.
The accident hadn't put him off cricket, Mr McKnight said, but the season would be over in a couple of weeks, so he will probably be on the side lines helping out.
Bay of Plenty Cricket chief executive officer Paul Read said as the policy stands helmets are not mandatory and in most cases are strongly encouraged.
In their view, helmets should be worn with any hard ball cricket and players are strongly encouraged to wear helmets at all times.
"I think if that can be reinforced through Karl's experience it's good for the game," Mr Read said.
New Zealand Cricket had been reviewing their policies and whether they were providing the right protection in terms of policy.
"If Karl's advocating we strongly support him and think it's fantastic he's taking that initiative."
