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When the UFC released Kimbo Slice in 2010, he knew his days in mixed martial arts probably weren't over.

What mattered was the opportunity. The man once known as The King of the Web Brawlers, who became an instant hit and launched mixed martial arts onto the prime-time airwaves for the first time, had been given just such an opportunity by the UFC a year earlier. UFC President Dana White had famously said that if Slice wanted to fight in the UFC, he'd have to work his way into the promotion by competing on The Ultimate Fighter reality show.

This was back when the UFC had the world at its fingertips, before it started signing pro wrestlers with zero fighting experience simply because of their name value.

But Slice didn't mind; he agreed to join The Ultimate Fighter and try to work his way into the UFC. Things didn't go all that well for him on the show: He lost to Roy Nelson in just about the worst style matchup he could have faced in the entire house.

Still, Slice graduated from the TUF house and fought twice in the UFC, beating Houston Alexander in a bout that was only memorable for Alexander's fleet feet before losing to Matt Mitrione. After his release, Slice was not presented with any opportunities, so he decided to take up boxing. He fought seven times from 2011 to 2013, scoring six knockouts.

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But then Bellator President Scott Coker approached Slice earlier this year with an offer: How would he like to come back to mixed martial arts and face Ken Shamrock?

"That was definitely a no-brainer," Slice told Bleacher Report on Tuesday. "S--t, I was on board from that right there."

The mention of Shamrock's name still brings an edge to Slice's voice, because they have a history that has never been fully resolved. And that's why the promotional name of Bellator's June 19 show headlined by Slice and Shamrock is subtitled Unfinished Business. For Slice, there is most certainly unfinished business.

"We have history. We went through something in the past," Slice said. "That was the start of me losing my first fight in EliteXC. And to have the opportunity to make up for that? I feel like he was the reason for all of that happening. Now I get to pay his ass back."

The "all of that" Slice is referring to is this, in case you haven't heard: On October 4, 2008, Slice and Shamrock were scheduled to headline an event for EliteXC in Florida. Hours before the fight, Shamrock allegedly suffered a cut while warming up for the bout. At the time, rumors circulated that Shamrock had attempted to hold up the promotion for more money and, when not granted his wish, had one of his cornermen or manager cut him intentionally.

With Shamrock out of the fight, the promoters scrambled for a replacement. They found Seth Petruzelli, an unheralded fighter who was more than willing to take on the late challenge. Keen observers knew that Petruzelli was better than Slice at mixed martial arts and would likely win the fight.

But Petruzelli still shocked most of the world a few hours later when he knocked out Slice just 14 seconds into the first round. It was also the beginning of the end for EliteXC, which put all of its eggs in the Slice basket and went out of business just a few weeks later.

It is clear Slice still holds a grudge from that night so long ago and that he relishes the opportunity to pay Shamrock back in the most violent way possible. But he also notes Shamrock's inability to fight that night, regardless of how it happened, might have been the best thing for The World's Most Dangerous Man.

"Shamrock would have just been another one of my victims," Slice said. "I really would have beat his ass like I'm gonna do now."

Slice said that he has improved dramatically in mixed martial arts. Though he did not participate in MMA training during his short-lived boxing career—because, in his own words, he "would have been tempted to kick someone or take them down when we were supposed to be boxing"—he continues to train daily at American Top Team in Florida and said that Shamrock may have missed his opportunity for a win.

"I was still a young wolf back then. I didn't have much of a mixed martial arts fight game," he said. "So if he had an opportunity to whip me, it would have been back then. Definitely not now. I have evolved over the years. I have developed a ground game. I'm just ready to go."

Slice said that the animosity between he and Shamrock is not manufactured. Even after seven years, he's still got a score to settle. At a recent press conference, Slice and Shamrock exchanged words, and afterward, Shamrock accused Slice of being disrespectful, though he would not share exactly what Slice said that angered him.

"He doesn't know what he's talking about, man. He just needs fuel for his fire," Slice said. "I'm dying for him to try and do whatever stupid s--t he's going to do, so I can knock his ass out. I'm going to put his s--t out and sit his ass down. That's what I'm going to do."

Jeremy Botter covers mixed martial arts for Bleacher Report. Follow him on Twitter.