Shane McGuigan will be a central figure in how the drama unfolds when Chris Billam-Smith challenges Lawrence Okolie for the WBO cruiserweight world title on Saturday night.
McGuigan has trained Billam-Smith for the entirety of his professional career and for a period of years coached Okolie, taking him to his first world title win and steering him through two successful championship defences.
Okolie left McGuigan's gym to join new trainer SugarHill Steward. They've had one fight together so far, Okolie's 12 round points over David Light in March.
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Now the champion's old sparring partner Billam-Smith becomes his challenger and at the Vitality stadium in Bournemouth they fight for Okolie's world title, live on Sky Sports.
Billam-Smith has traded plenty of leather with Okolie in sparring and has all McGuigan's extensive knowledge of his opponent to draw on as well.
That could be decisive.
Okolie is a hard man to beat. He has size, strength and power as well as good understanding of how to win rounds. He might only have had 19 pro bouts but the former Olympian is an experienced fighter.
McGuigan though believes he has identified areas where Okolie can be beaten.
"His weakness is mindset," he told Sky Sports. "He doesn't fear or shy away from combat. It's just he sees himself as a business. So if this business gets derailed, his value goes to nothing and his mindset thinks I instantly go back to working a job if this fails.
"That's Lawrence Okolie's mindset: 'I've got to win this and I'll win it no matter what. I don't care if people are booing, I'll still get the W.'
"I spent just over three years fine tuning those skills," McGuigan continued. "But that also gives me an understanding of who he is and what he does well and what he doesn't do well.
"There's not as many physical weaknesses with Lawrence, more mindset weakness. I feel like he loves someone to rile him up.
"He struggles when someone's respectful. He gets lulled into that friendly environment."
Okolie's size, McGuigan also argues, can be a disadvantage.
"He's just too big for the weight. He's far too big for the weight, he's 30 this year, it's taking away from his performances. It's taking away that snap and that vigour and the reason he's doing that is he doesn't believe he's going to be as effective at heavyweight. So that's a weakness in his mind, [thinking:] 'I have to boil myself down so I have an advantage, so I'm bigger than them,'" he said.
"If Lawrence genuinely believed he could do it at heavyweight, he would have moved up to heavyweight by now."
But McGuigan and Billam-Smith also know how dangerous Okolie can be.
"I chose to work with Lawrence because I rate him so highly. He's got great punching power. He's got great athleticism. He's got a good boxing brain as well," McGuigan said.
"That [mindset] is Lawrence's weakness and also his feet. Having to adjust all the time, it takes away his power. For us we have to make the right adjustments that he doesn't set for too long. When he sets, he's dangerous.
"We've done so many rounds with Lawrence and we've seen him do so many rounds with other styles, I know what style he struggles with. That being said we've got to try to come up with the perfect gameplan and execute it for 36 minutes."
McGuigan is adamant that Billam-Smith can do just that.
Billam-Smith would have been considered an unlikely candidate to become a world champion when he turned professional. He has continually exceeded expectations, having now won British, Commonwealth and European titles.
Tonight Billam-Smith has a shot at his ultimate goal in his hometown, even if it does come against an old friend.
Consistent professionalism, McGuigan explains, is what has allowed Billam-Smith to excel.
"He strives for one percent better every day, it's small wins every day for Chris," he said.
"It's: I'm going to figure out the best way to warm up. The best way to sleep. He wears blue light blocking glasses, he puts mouth tape on when he goes to sleep so it forces him to nasal breathe. He does so many add ons that over time it's just compounded into making him such a better athlete.
"If he wins a world title it's monumental, it's massive. It would definitely be my greatest achievement as a coach.
"I've had two-weight world champions, I got George [Groves] over the line on his fourth attempt but where Chris started out and where he is now, it's the biggest success story.
"Either way I'm really proud of him."
Counter-intuitive perhaps, but to dethrone Okolie McGuigan believes Billam-Smith will have to keep him throwing punches to avoid getting tied up on the inside.
To win in other words he thinks the challenger needs to make it exciting.
"It's going to be a great fight. Chris will not allow him to kill the clock. I hope we get a good referee who doesn't allow him to kill the clock. It's going to be an explosive fight," he said.
"I believe the two of them can hurt each other. The power doesn't just lie with one fighter, with Lawrence. I feel like of the two of them Chris' power is really underrated and they can both hurt each other on different ranges.
"So it's going to be an exciting fight. I'm not sure it will go the distance and I'm hoping and believing that Chris gets the victory.
"Lawrence is very good at nicking rounds with his size," he added. "We're going to knock him out. Head or body.
"Let's go."