Nearly eight years ago, “The Ultimate Fighter” rolled out a unique twist for the 20th season of the reality series that helped rocket UFC to the heights it has reached today.

“A Champion Will Be Crowned” crowed the season’s subtitle. Indeed, the fall 2014 season would be the first to determine a UFC champion, in this case for the newly announced strawweight division as the promotion’s second for women — a year after Ronda Rousey shattered the glass ceiling. 

Two months of filming and, later, three months of weekly episodes made clear two things: Top seed Carla Esparza was worthy of that status and prospect Rose Namajunas was the future at 115 pounds. The future had to wait, as 27-year-old Esparza tapped out the 22-year-old Namajunas in the December 2014 tournament final.

That a rematch would one day happen wouldn’t have surprised anyone at the time. That it took nearly 7 ½ years before the two would stare across the octagon from one another, on the other hand, is a stunner. But that’s exactly where Namajunas (11-4, seven finishes) — by now a two-time champion — and challenger Esparza (18-6, eight finishes) find themselves entering Saturday’s UFC 274 ESPN+ pay-per-view co-main event at Footprint Center in Phoenix.

Following the loss to Esparza, Namajunas naturally faced less experienced competition than the former Invicta FC strawweight titleholder. By November 2017, she’d won four of her last five to earn a title shot against Joanna Jedrzejczyk, who’d spoiled Esparza’s first title defense just three months after “The Ultimate Fighter.” It was a star-making performance as Namajunas picked up a first-round TKO victory.

While Namajunas has competed in five of the last six strawweight title fights — winning four and having regained the belt from Zhang Weili last April — Esparza appeared to fall out of the mix with back-to-back losses in 2018. That’s when she lost consecutive fights to top competition: former title challenger Claudia Gadelha and blue chipper Tatiana Suarez. 

The Suarez fight, ending in a third-round TKO stoppage, was a wake-up call for Esparza. The result “wasn’t acceptable.”

“I was in shock,” Esparza recently told The Post over the phone. “I was like, ‘Damn, I have some things I need to fix. I need to really take a step back and go to the drawing board and analyze where my faults are, why I’m losing.’”

Esparza reinvented herself technically, physically, and mentally. The former NAIA All-American wrestler studied her defeats and lost rounds to discover why she kept finding herself stuck on her back in recent fights. She worked at Team Oyama to refine technique everywhere, including her striking. 

Noting that she isn’t a large 115-pounder, she worked with the UFC Performance Institute to add strength and build herself into a strawweight of “at least comparable” size to her competition.

Negative thoughts had filled her head in the past, but a change in mindset helped her to start “believing in myself more and envisioning my success.”

“I would look at other people, and I would look at how good they were or what I was doing wrong,” Esparza said. “Instead, it’s like, ‘No. I can do this. I have the skills. I’ve just gotta put the work in.’ Just really changed my mentality, and it helped me a lot.”

Desired results followed, with Esparza rattling off a five-fight win streak with narrow decision victories over Alexa Grasso, Michelle Waterson and Marina Rodriguez before securing the first TKO victory of her UFC career last May against Yan Xiaonan — the first finish since she beat Namajunas.

“It was amazing, and it couldn’t have come at a better time,” says Esparza, now 35. ”I felt like it really made a statement, and it really solidified me to take this next spot for the title.”

Namajunas agreed, believing Esparza earned her way back to the unlikely rematch. But the 29-year-old champion has yet to lose any of her previous four rematches, including three in championship fights. It’s sort of a specialty for “Thug Rose.”

Learning from mistakes is key to that, Namajunas says.

“Growing up, I always had a fear of making the same mistake twice, ‘cause I would get slapped upside my head if I did,” laughs Namajunas while speaking with The Post on a recent Zoom call. “So it’s one of those [situations] of avoiding sticks and chasing carrots.”

Admittedly, Namajunas’ run as on-and-off champion the past five years didn’t have a second meeting with Esparza near the front of her mind. She’s the type to focus squarely on the opponent in front of her, but moreover Esparza had not been one of the top handful of strawweights for many years until recently.

“She’s been kind of lingering in the background the whole time, whereas I haven’t really had my eyes set on her the whole time,” Namajunas said. “But I know that she’s been grinding and racking up those wins.”

Competition in the strawweight division has grown since its 2014 UFC introduction. Not that it didn’t exist before that — with Megumi Fujii and Jessica Aguilar among the early greats — but iron has sharpened iron, so to speak, and forged a highly competitive weight class.

Esparza contrasts her win over Namajunas with their respective recent fights to underscore the evolution of the 115-pound women.

“The skill level of the women has come so far,” Esparza says, marveling at the collective progress. “I think it was good then, but I think it’s the same kind of path that the men have taken. If you watch UFC, the first few [events], it’s really evolved, the level of the athletes.”

Namajunas, who consistently has faced elite opponents for roughly half of her career, highlights the strength of the upper crust that she’s as familiar with as any woman in the world.

“The level of the top five people in the strawweight rankings are pretty solid as far as, once you break into that top five, the competition is really, really fierce,” Namajunas said. “Over the years, you’ve seen the cream rise to the top. … With another successful title defense, that would definitely solidify who is the creamiest of the cream of the crop.”

With so much time elapsed since the first fight, Namajunas doesn’t look at this rematch the same way as the others — she faced each of her last three opponents (Jedrzejczyk, Jessica Andrade, Zhang) back-to-back. She views Esparza as a new challenge given how much each has changed since 2014. But ultimately, her focus is on racking up title defenses one at a time, and this fight simply is the latest challenge.

Esparza, meanwhile, chases a second chance at being a champion. She says she barely had the chance to soak it in last time before losing the belt in March 2015 and doesn’t think she even had the chance to show her family the belt while she was on top.

Championship gold would look mighty nice as part of Esparza’s wedding ensemble the following weekend. The timing of two of the biggest days of her life has understandably made life “pretty hectic,” but she says she got ahead on planning her nuptials early in the process.

Some impressive history could be in store for Esparza as well. With 2,703 days elapsed from the date of her win against Namajunas to Saturday’s fight, a victory would shatter the record for longest gap between wins in UFC championship bouts. Frank Mir won the interim heavyweight title 1,652 days (about 4 ½ years) after first winning the undisputed crown — and subsequently relinquishing the title following a motorcycle accident.

When The Post informed Esparza of the potential accomplishment, she perked up at the thought of what that particular history-making win would say about her journey back to the top.

“It’d be hard for someone to come and take that spot,” Esparza said with a stunned laugh. “Oh, my gosh. That would be super cool. I think it would say so much about how far I’ve come in this time and been able to maintain my position in the division for so long. That would be so huge.”