An alleged unprovoked king hit that knocked the nephew of a former All Black unconscious forced a Hawke's Bay rugby game to be called off early by the referee.

The Saturday game Waipukurau between reserve grade teams Napier Technical and Central Rugby and Sports ended in ignominy as Central player McKenzie Oliver, 20, was struck from behind by a Napier Tech player, who has since been stood down from the team.

Oliver was knocked out "cold" before he was taken by ambulance to the Emergency Department at Hawke's Bay Hospital for scans.

He has been diagnosed with concussion and stood