"He woke up on the way to the hospital," Legg said.
Legg wouldn't give specifics on the health status of the fighter beyond saying "last I heard he was doing really well".
"He's had the brain therapy stuff but he's sort of come good now. He's running and he's all good," Legg said.
A fellow fighter in a separate bout that night, Maddie Brogan, said the incident was "traumatic" for the audience and the entire night was cancelled following the knock-out.
"It sort of got hushed up. Because it happened so suddenly it was traumatic for everybody there. People didn't really want to fight because this guy got super injured.
"It was out of nowhere, and we didn't really know how serious it was until he wasn't moving at all and then everyone jumped on stage."
Brogan said some spectators feared the injured fighter would die.
News of the serious concussion at Boxing Alley in April has emerged just days after a 31-year-old Wellsford woman died after suffering a head injury during a sparring session.
Mother of two Lucy Brown died on August 22 after she was flown to Auckland City Hospital in a critical condition having collapsed during sparring at Wellsford Boxing Sport & Fitness Club on August 18.
On September 24, 2016, 49-year-old Hamilton man Neville Knight was also killed during a charity boxing match.
Knight's fiancée administered CPR on him for 30 minute, and his son carried his body from the ring into a waiting hearse after he was declared dead.
Harry Otty is an Auckland amateur boxing coach with 30 years experience who has trained boxers vying for the Olympics and currently works under the Shamrock Boxing Association.
"I'm not a big fan of corporate boxing to be honest with you because you can't play box. You can play football, you can play tennis, you can't play boxing," he said.
"In my opinion I don't think you can learn to box in 12 weeks."
"You don't really know what you're getting because there's too many variables. You could go to a corporate event anywhere in the country and one boxer will have shorts, singlet and a head guard on, and the other boxer will have no singlet, no headguard."
Senior neurosurgeon at Melbourne's Alfred Hospital, Professor Jeffrey Rosenfeld, said being knocked unconscious for 20 minutes was a "significant time".
"Certainly if you have a number of concussions that are of the order of 20 minutes of unconsciousness then you are putting yourself at risk of having permanent brain damage," Professor Rosenfeld said.
"When you have a 20 minute loss of consciousness there is internal damage or derangement in the brain and in some people that can reverse completely, and in others it doesn't. There's a lot of individual variation.
"The objective of boxing is to render your opponent unconscious, there's no other sport like that. The starter gun has gone off for him [injured Boxing Alley fighter] on whether he will get longer term problems."
Former New Zealand champion boxer and NRL star Monty Betham works at Boxing Alley running corporate training sessions.
He said the incident rattled Legg and they had not held a similar event since.
"No they haven't done one since because I know they spent some time right beside the person who had the problem within the corporate event and he [Legg] was worried," Betham said.
"It definitely shook him up you know, and it would."
However, Betham said safety precautions in place during Boxing Alley events were of the highest standard.
"I've had fighters at events that they put on. They do everything very well, the best training, all the right equipment, the fighters are fit. So it's just one of those ones."
