It was several moments after losing her first fight as a professional when Mikaela Mayer finally let out her emotions.

“The second I got away from it, like the crowd, I just started bawling,” she recalled.

“You want to go back in time, wake up, but you can’t. It’s done, you can’t recall this decision.

“You can’t replay the fight and ask for a second opinion. You can’t do anything…it’s just over.”

Mayer had not lost since her amateur days in 2017. She was 17-0 as a professional when she stepped into the ring with Baumgardner. It was a close fight, one Mayer started slowly but managed to take control of in the second half.

The first scorecard read out was 97-93 for Mayer, the other two judges scored it 96-95 for Baumgardner.

“When they announced that second score for her, I knew right away they were going to rob me,” Mayer said.

The 32-year-old was as furious as she was confused. Advised to stay in the ring by her publicist, Mayer remembers, vaguely, Baumgardner approaching her to say well done.

But it is all still a blur.

“I’d never been in that position before so I wasn’t sure exactly how to handle it,” said the American.

Mayer went back to her hotel that night with her best friend Ginny Fuchs. A fellow boxer, Fuchs had won her own fight. They ordered pizza, cracked upon a bottle of wine and “just sat there”.

Mayer was grieving then. She and compatriot Baumgardner, 28, had feuded for months in the build-up to the fight. Both supremely talented, they made no secret of their dislike for one another.

It was a heated rivalry and Mayer returned to the United States, but she was devastated.

“You think that your life and your story is now theirs,” she explained. “That they’ll go on to accomplish everything that you wanted to do.

“Or maybe another scenario is everything that was said in the trash talk was right and everything I said was wrong.

“Those scenarios are just running through my head all day long and basically what happens is my heart just drops to my toes every 10 minutes of the day.

“How am I going to get through another day of this?”

Mayer spent the next three weeks going through this rollercoaster. She not only questioned herself, but her future.

“I always thought the second that I lost, or if I ever lost, how would I pull myself together for another training camp? How would I keep going?” she added.

But then, slowly, Mayer began to think clearly. She still had the support of her partner, her promoters Top Rank and trainer Al Mitchell.

“The depression starts right away,” she said. “You feel like it is never going to go away and then you just start to adapt.”

Mayer realised she did still have the fire to fight.

“I’ve always wanted to put on the biggest fights possible and this time I came up on the short end of that,” said the Californian.

“But it doesn’t change the goal. I still want to make the biggest fights possible.

“I still feel that’s important and I can’t preach that and then. When it’s time for me to do it and believe it and walk the walk, I can’t sit back and cower.

“I know one day I will wake up and say I’m glad that happened. If it didn’t happen I wouldn’t be where I am today. Eventually it turns out OK and it’s not the end I thought it was.”

Mayer subsequently instructed her team to find her next opponent and has targeted Ireland’s undisputed lightweight champion Katie Taylor or Belgium’s top contender Delfine Persoon.

Obviously, she wants a rematch with Baumgardner, but that seems unlikely for now as her rival chases an undisputed contest with South Korea’s WBA champion Hyun Mi Choi.

The bout with Baumgardner was chief support to Claressa Shields’ undisputed middleweight fight with Savannah Marshall. It was the first all-female card in the UK and the first time women fighters had headlined at the O2 Arena.

Sky Sports said two million people watched the fight night – the broadcaster’s biggest-ever audience for a live women’s sports event.

Now Mayer sees her encounter in a totally different light.

“It was the highest point in my career and lowest of my career,” she reflected. “In such a short amount of time I got the most respect and appreciation, eyes and views that I’ve ever got and on the biggest stage, to the lowest of the low.

“When I set out on this dream, that everyone said I was crazy to go after, this is what I always envisioned and hoped for.

“It can’t be one loss and your whole career is shattered and devastated – and over.

“I believe that is true for us women. I don’t necessarily believe it’s true for the men, so props to us – props to the sport we’ve created.”

Mayer believes she could fight Baumgardner three times, if not more in her career, seeing it as a “once in a lifetime rivalry”.

She is ready to continue taking the biggest fights and insists women’s boxing can set examples for the sport’s future.

“I just want to continue to set a new tone for boxing and be a part of that – and that’s why I had to crawl out of my hole,” added Mayer.

“I think this new era of women’s boxing is going to set the tone for boxing and how it should be done.

“The only reason is because we didn’t have the luxury of turning down the big fights and sitting back on our million dollar pay day and picking them.

“We had to put our ass on the line and make the big fights, just to get the respect.

“And look, it worked. Me and Baumgardner, Taylor-Serrano, Marshall-Shields and all the other undisputed fights.

“It wasn’t just one or two of us doing it, but so many of us. We came together to fight for what we believe in.”