Don't expect insults, expletives and antics before Dustin Poirier and Justin Gaethje get in the Octagon at UFC 291 ... 'cause the Diamond tells TMZ Sports their BMF title fight is nothing personal -- they actually have a lot of love for each other.
Poirier and Gaethje -- the second and third-ranked lightweights in the standings, respectively -- are set to fight each other for the first time since 2018 this weekend ... and both guys had high praise for each other in the days leading up to the showdown in Salt Lake City.
"It's a mutual respect," Poirier said. "Every time he fights, I'm watching. I love watching his style. You earn a different style of respect for someone after spending 20 minutes bleeding in an Octagon with him. Even though it was five years ago, I still remember it. And I'm excited to do it again."
DP says his opponent has gotten better and changed his game since their first meeting ... and now, he's expecting an entirely different fighter.
As for pre-event shenanigans, Diamond says that's entirely unnecessary ... 'cause any MMA fan knows what to expect Saturday night -- and he's going to put on a show en route to securing the belt.
Gaethje is equally pumped for the matchup ... and he told us adding the BMF title to his collection will be big for his legacy.
Poirier won the first fight, and the Highlight told us he's hoping to avenge his loss and get back into championship contention.