It's time to address the elephant in the room.
That thought isn't really intuitive—when Belfort's name comes up, you're more likely to remember him as the TRT-fueled knockout machine of 2013, the middling version who existed outside the UFC for much of the 2000s or, if you've been around long enough, the first proper phenom the sport had ever seen back in the late 1990s.
You kind of assume he'll be around forever.
Except he won't.
Realistically, the clock has been ticking for a while, and it might tick its last tock against Gastelum.
Belfort, since TRT was functionally banned, has not looked great.
He's been violently smashed in three of his last four bouts, stopped viciously by TKO in each loss. His only win in that time was over Dan Henderson, who was well past his prime and has since retired. He's a 39-year-old veteran who once relied on speed and explosiveness that are rapidly declining, and who's lost as many times since 2015 as he had in the previous seven years.
It's the type of track record that doesn't lie—when a veteran mixed martial artist starts to go this way, they don't often go back. Age gets everyone, and when you've been warring with the killers of three generations of the sport, there's absolutely no doubt it's going to get you too.
Henderson left at 46, 3-7 in his final 10 fights. He never once looked as formidable in those bouts as he did in his prime.
Belfort nemesis Anderson Silva, nearing age 42, narrowly beat Derek Brunson at UFC 208. To say that wouldn't have been the case five years ago doesn't even remotely do the outcome justice.
Legends such as the Nogueira brothers or Mauricio "Shogun" Rua (who is also fighting at Fight Night 106) either retired too late or are still fighting to limited positive effect, and they are wearing the damage as a result.
Continually it's been proven that MMA is a sport that waits for no one.
Regardless, there's always been something fascinating about the way Belfort fights. He is, even now in his diminishing form, as vicious an attacker as the sport has ever seen.
Nobody has the finishing instinct he does, the ability to see even the slightest hint of injury in his opponent and then pour on violence until the fight is stopped and he's declared the victor. In many ways, that's what his legacy will be, alongside being a UFC tournament winner and world champion who challenged in multiple weight classes while remaining relevant long after most of his contemporaries had gone home.
That's where Belfort finds himself, clinging to his beloved old lion analogy as he prepares to face an up-and-comer unlike any he's faced since he was a young man himself.
Gastelum is nasty business, a former welterweight who just retired Tim Kennedy a few months ago and who'll look to do the same to Belfort. He's just broken into the top 10 at middleweight and has the tools to be something special, a man who shows considerable improvement every time out.
It all adds up to serve as a source of concern if you're a fan of Belfort or MMA's old guard.
It serves as a source of curiosity if you fall into some other group as you watch on Saturday: Can Belfort, who is 5-1 in Brazil, hold his home turf one more time? Or is Gastelum the young lion who's about to rise up and snatch Belfort's spot in the middleweight pride from him?
It's no certainty, but based on the history of those old lions and how long they generally hold out before time catches up to them, one would have to think Belfort is getting close to the end of the line.