The main event at UFC 270 will see heavyweight champion Francis Ngannou face off against interim title holder Ciryl Gane in a much-anticipated battle.

Not only will this be a meeting of two of the most dangerous fighters on the whole UFC roster, but also a clash of former training partners at MMA Factory in Paris.

Head coach Fernand Lopez was the man who introduced Ngannou to the sport, helped him break into the UFC and oversaw his rise to heavyweight contender.

Their relationship has soured in recent years, though, as Ngannou left MMA Factory to train at Xtreme Couture in Las Vegas, with Gane - who is the in the online betting to win at UFC 270 - taking his place as Lopez's UFC hope.

Now, ahead of the fight in Anaheim, Lopez has spoken out about the deterioration of his relationship with Ngannou, and admitted that he regrets the way things have gone between them.

"Absolutely, I do regret where things are between us," he says. "The truth is, I regret the situation between me and Francis. I have a bunch of other students that I have fallen out with in the past and we’re still friends and still call each other. But because of what’s said in some media - I don’t like this, it makes me look bitter - I look like someone who will not let Ngannou go.

"I did not call journalists and say: 'can you call me about Francis, I want to say a bad thing about him.' No, I'm over it. But I do regret it because our story was actually very beautiful.”

After making his way to France from Cameroon at the age of 26, Ngannou was sleeping on the streets of Paris before Lopez took him in to his gym, gave him a place to sleep and taught him mixed martial arts. 

The two spent many years together as Ngannou made his way from MMA novice to UFC contender, but Lopez says he doesn't miss the company of his former protege.

"Do I miss Francis as a friend? No. I don’t think you can quite be friends with Francis. I don’t think you can miss him as a friend," says Lopez.

"He’s not family but he’s a cool guy. We’d spend five days together in a room without speaking much, just: 'are you ready to train?' and then when we go back and I'd say 'do you want to go out?' - we weren't speaking that much.

"Only sometimes he would have inspiration and speak for like two hours telling me his way to Paris from Cameroon. He was so passionate about the journey, but he’s a guy you don’t miss. But again, I do regret the relationship now.

"I told him to get out of my gym three times. The mindset that he had was not the mindset of my gym. I didn’t want him at my gym anymore. But that’s not to say there wasn’t anything great in our relationship. We had very good times and that’s it. But it was good to have him out of my space because of the toxicity of the relationship.”

"Let people know where I stand," he explains. "I was telling my girlfriend the other day: I’m a guy that likes to be nice to people. Francis Ngannou has a lot of fans and his fans look at me like a guy who is bitter and who is bad for his career. I am not here to do that. I hate that.

"I am not a bitter guy, I'm over it. How can you not be over when you have the best guy? If Francis was the best fighter maybe I’d have a reason to be jealous, but I have the best fighter. Ciryl is the best fighter, the best mindset, the cooler guy - why the hell would I be jealous?

"Who would want to be close to Francis right now? The UFC cannot stand him, why should I be jealous of that. I’m a guy who talks with passion but I’m not a guy who wants bad things for Francis.”

As Ngannou's former trainer, Lopez is in a unique position to understand the areas that Gane may be able to exploit at UFC 270. 

As well as any mental weaknesses, Lopez claims that Ngannou is struggling with a back injury heading into the fight.

“I know him and he knows me, we know each other well," he says. "I spent many nights with him in the same room, I spent time with him on flights, I spent a long time with him in the gym.

"I know his pain, his medical background, I know what wears him down, I know his back problems - I know he’s hurt in the lower back. I know if you get him in a certain position it will wear him down because he has big pain in his back.

"I know his mental weakness because I saw him in the changing room after his first loss. I was the one pulling his shorts so he could breathe properly.

"There’s nothing else Francis can do but put Ciryl under pressure. Francis will need to be calm, but he cannot be calm and when he puts the pressure on, it will leave gaps in his game.

"It’s about mindset. Ciryl and Francis need to concentrate, the one that makes the mistake will go down. I don’t see this one going the distance, someone is going down.”

In Lopez's eyes, there is only one outcome to the fight - a knockout win for the challenger.

"I don’t see how you beat Ciryl Gane unless you put him under pressure," he says. "So I think Francis will try to put him under pressure, and when he puts Ciryl under pressure, this is the time he leaves himself open.

"Either you decide to be conservative and you play safe then you might lose the decision. Or you rush, and if you rush, you better not make a mistake, because there’s a sniper out there in Ciryl.

"If you rush you might give Ciryl the knockout. He might not be a knockout artist, but if you combine the acceleration of Francis’s attack with Ciryl's heavyweight power, Francis will wake up after the fight.”