The bantamweight headliner is a rematch of a close, three-round contest from June 2017 and should have major implications on the 135-pound title picture. Assuncao won the first meeting via split decision.
Here's everything you need to know about Saturday's UFC Fight Night, courtesy of ESPN's Cheat Sheet.
Raphael Assuncao (27-5) vs. Marlon Moraes (21-5-1), bantamweight
Odds: Moraes -175; Assuncao +155
This 135-pound main event looks like a No. 1 contender fight. It absolutely should be a No. 1 contender fight.
But is it? Will Saturday's winner actually face TJ Dillashaw for the bantamweight championship next? Just listen to these responses from both, and you be the judge.
"I think about that Johnny Cash song: You can run on for a long time, sooner or later God'll cut you down,'" Moraes told ESPN. "I don't care if I'm going to fight TJ next or not. I can beat all these guys. One day, he will have to fight me. I'm here to work and I'll fight anyone after this."
"I have no control in that," Assuncao said. "I have no say."
That's all the proof one needs to know the UFC's bantamweight division is a little out of sorts right now. Assuncao has won 11 of his past 12. Moraes, 16 of 17 -- and yet, neither is confident he'll fight for the title next.
Dillashaw (16-4) is coming off a failed attempt to move down in weight and capture the flyweight title. He lost to Henry Cejudo in just 32 seconds earlier this month, and there seems to be momentum behind an immediate rematch -- this time for Dillashaw's belt.
That definitely has added some uncertainty to Saturday's rematch. The first fight between these two was not particularly entertaining -- so, the only reason to even have a rematch is to shake out the next title contender. However, it doesn't feel as if that's on the line.
But sometimes in this sport, it's not about how much a win will elevate you -- it's about how far a loss will drop you. And that is the case here. Assuncao and Moraes have been nearly perfect in recent years -- and still a title fight has eluded them. Neither can afford a loss this weekend.
How much has changed since the first time they fought? Has anything changed?
To me, this fight looks the same as it did 19 months ago. The biggest advantage either has is Moraes' speed. He is simply much quicker than Assuncao -- but Assuncao seemed to get more comfortable with that as the first one played out.
If the rematch looks similar to the original -- in that it turns into a technical stand-up battle -- it's hard to not favor Moraes. He's more of a finisher. He's lethal from the outside with kicks, and that speed advantage really helps him counter Assuncao effectively.
The onus to make adjustments falls on Assuncao, which sounds odd considering he won the first fight. To beat Moraes again, however, Assuncao may need to back him up more. Set a higher pace and get in Moraes' face with that right hand. Mix in a takedown or two.
Does a five-round fight benefit one more than the other? Not dramatically. Moraes has recorded a finish in 72 percent of his career wins. Give someone like that an extra 10 minutes to work -- against an opponent who has finished only 52 percent of his wins -- that's a positive.
But Assuncao is incredibly savvy and knows how to win. He's had five split decisions in his career, and gotten four of them to go his way. And if he does turn up the pace on Moraes in this rematch, as I believe he probably should, that could have a cumulative effect late.
Prediction: Assuncao by decision