Thirty minutes later he was rushed to Waikato Hospital, where a surgeon opened his skull to deal with bleeding on his brain. He was placed in an induced coma, his life hanging in the balance.
MacKinnon not only lived, but lived up to the stories about his incredible toughness. By Monday morning he was conscious and cracking jokes.
"He's a country boy from Otorohanga," MacKinnon's friend and sparring partner Shane Cameron said. "Anyone who comes from the country tends to be pretty tough. And boxing is not for the faint-hearted."
Nor the cold-hearted. The boxing community has rallied around MacKinnon, who still faces a long, hard road to recovery. A chef by trade, the 30-year-old father of three also works as a trainer at Cameron's North Shore gym. He's unlikely to be able to work for some time, so a relief fund been set up to help his family.
His toughness may be legendary but MacKinnon is also one of boxing's nice guys. He never fought out of his local King Country Boxing Club - father Ken was responsible for his early development - but MacKinnon is always on hand whenever he's needed at the club that sits in the middle of nowhere, 8km out of Otorohanga on State Highway 31.
"He's an awesome guy all around," says club founder Glenn Brightwell. "When I need young fellas to get a bit of inspiration I call him in."
The MacKinnon family have rebuffed all requests for interviews, saying through spokesman Ken Reinsfield their focus is solely on being there for Daniel. That doesn't surprise Brightwell.
"I have known Daniel for many a year and the biggest thing about him is he is a real family man. He's got awesome kids. Man, they are a crack-up. And he loves his kids more than anything. That was one of the first things that came to mind. To think he would never be himself again would be quite a frightening thought for his wife and children."
The signs for a full recovery are positive. MacKinnon is walking and talking, something many fighters who incur similar injuries never achieve.
Cameron knows of two other Kiwi fighters who have suffered serious head injuries during his 15-year career. Neither of them, he says, is in a good way.
Cameron wasn't aware of his gym mate's drama on the night. MacKinnon was supposed to join him at his ringside table for the David Tua fight that was the night's main event but that never happened.
When Cameron did finally hear how badly MacKinnon was hurt it hit him hard.
"It was a massive reality check," he said. "When it happens to someone you know pretty well it brings it home that it could happen to anyone at any time."
In three weeks, Cameron will be back in the ring himself. The positive news about MacKinnon has made getting his head around that a bit easier.
"I spent a couple of days just thinking about Dan. It's good for me to hear that he is coming right and doing really well."
MacKinnon's injury has been described as a freak occurrence. But many of the ingredients that have led to similar and often more tragic outcomes were there.
His previous two fights this year were both tough 12-rounders, one a split decision win, the other a majority decision loss. The 10 rounds against Berridge took him to 34 rounds in nine months.
MacKinnon desperately needed a win, and there was antipathy between the fighters. Berridge is a huge puncher so MacKinnon was expected to use his skill to stay out of trouble. Instead he traded punches, showing huge heart but fighting, if anything, too bravely.
The fight has been described as one of the best, and most brutal, of recent times.
"It was certainly a crowd-pleaser," Cameron said. "And that is what you are doing in the ring, entertaining a crowd."
MacKinnon, Cameron insists, will have few regrets at going all-out in an attempt to crack the boxing big time.
"He wanted to give it a good nudge. Your career is only so long and if you are only doing it half-pie you get half-pie results. "
It didn't take long for news of MacKinnon's predicament to reach Brightwell, who feared the worst.
"It scared the shit of me when I heard it," he said. "To hear him come through it was really good."
A small country club with "a shitload of heart", the King Country Boxing Club has only two active fighters. MacKinnon, Brightwell says, will be back helping out as soon as he can, but he doesn't expect him to ever fight again.
"He loves boxing but he loves his family more."
To donate
Dan MacKinnon relief fund
• Facebook: Dan-MacKinnon-The-Return-of-The-King
• Donate directly into: 03-1562-0414701-00
• Or at Westpac branches
