A boxer is in a critical condition after being knocked out while sparring in Wellsford.

The woman, believed to be in her 30s, suffered a head injury during boxing training at Centennial Park.

Auckland Westpac Rescue Helicopter crew responded to the call at 11.34am.

Westpac pilot, James Tayler said, "[she] suffered a blow to the head, was initially concussed, but generally felt OK at first.

"Her health deteriorated rapidly from there."

The patient lost consciousness before the helicopter arrived. Westpac crew performed a Rapid Sequence Intubation (RSI) to assist her breathing.

She was flown to Auckland City Hospital in a critical condition.