Nov 11 - Once an underground combat sport, bare-knuckle boxing has followed the way into the mainstream paved by mixed martial arts, and professional fighters now find themselves with greater possibilities than ever before.

Saturday's card at London's O2 Arena, promoted by BKB, will showcase some of the best British fighters in the sport, with Aaron McCallum one of those who will be wrapping his fists in thin gauze before his welterweight rematch with Simey Doherty.

"If you look at how fast it's grown now, I dare say in two years max it will just blow everything else out of the water," McCallum told Reuters.

"It's going to be everywhere - the advertisements will be all over billboards, it'll be all over your normal adverts on TV channels. They're doing the (Anthony) Joshua (Tyson) Fury (boxing) fight now, advertising that, and I dare say that in two years, the big fights in BKB will be scattered everywhere."

The rise of the sport coincides with a time when some fans see traditional boxing fights as becoming boring, with an emphasis on defensive skills and footwork rather than knockout power leading to many high-profile bouts going the distance.

"In gloved boxing, for me, every fight's the same now, it just goes on and on and on. With bare-knuckle, you do not know what's going to happen in any fight," McCallum said.

BKB's style and rules are designed to leave nowhere to hide.

Consisting of a maximum of six three-minute rounds - or half as long as a top-level boxing match - BKB fights take place in a triangular ring that effectively keeps the fighters toe to toe for the entire bout.

CUTS INEVITABLE

McCallum took up the sport when he retired from bodybuilding and said that the lack of padded gloves means that cuts are almost inevitable in bare-knuckle boxing, but that the risk of concussion is lower than in regular boxing.

"I've had a few injuries myself, I'm not going to lie, but I recover fast, and you don't really recover as quick in gloved boxing," the 40-year-old from Nottingham said.

McCallum's view is backed up by a presentation made to the California State Athletic Commission in March by doctor Louis Durkin, president of the Association of Ringside Physicians, as BKB sought a license to stage a test event in the state.

Meeting minutes show that Durkin told the commission that "while the laceration rate in bareknuckle boxing was much higher than in boxing or MMA, the concussion rate was much lower".

Though BKB has staged shows at the O2 in the past, McCallum said that he has noticed a marked increase in interest of late.

"I remember only six months ago telling people who just met me that I do bare-knuckle professionally, and they were like, 'You what?', but now when you say it, they know it, they know it's professional. It's just gotten quite big," he said.

McCallum explained there are now young, hungry pro boxers switching to bare-knuckle early in their careers because of the opportunities it can offer, but he still has his sights set on winning a world title and cementing his legacy as one of the sport's pioneers.

"There's been a few fighters from Nottingham that's fought bare-knuckle on the scene, but nothing like what I'm doing now, so a lot of people have got a lot of respect for me and what I'm doing," said McCallum, who is on an undefeated run of four fights that include a draw in his previous meeting with Doherty in London in July.

"My following's massive now... You just want to imagine where it is right now - I mean, it's going global." REUTERS