We often hear fighters approaching retirement announcements cautiously, peppering terms like “for now” and “if,” almost so as not to make too definitive.

You won’t get that from 15-year MMA vet Thales Leites (27-9 MMA, 12-8 UFC), though. After he leaves the octagon at Ibirapuera Gymnasium in Sao Paulo, where he meets Hector Lombard (34-9-1 MMA, 3-7 UFC) at UFC Fight Night 135 on Sept. 22, Leites has made his peace with the fact that will no longer be an MMA fighter.

“It’s not an idea,” Leites told MMAjunkie. “It’s been decided. I will do my last fight and I will stop.”

The decision, Leites says, has been in the making for about a year. And while he understands why fellow retired fighters would get the urge to return after being away from the cage for a while, he just doesn’t think that’s something that will happen to him.

That might be because this wasn’t a decision triggered by a specific event – like, as it’s often the case in these situations, a bad injury on specific lingering damage. His body, Leites says, is holding up just fine. But the Brazilian middleweight also knows he’s asked a lot from it after not only 36 professional fights, but also the gruelling training camps that before so many of them.

It adds up. And while he feels healthy now, he wants to give his body a rest in order to make sure that’s the case in the future, as well.

“I’m going to be 37, I already have a pretty big number of fights,” Leites said. “I don’t want to stay at 37, 38, 39 doing this very intense training that also has a lot of impact to the head – the famous concussion. Like it or not, every training session, you’re taking impact to the head.

“Not to mention the abrupt weight cuts. Doing that two to three times a year, we know it’s not healthy. It’s needed in the sport, and it’s common – of course, we do it with medical guidance, and we’re used to it. But how is the future of the athletes who started doing these weight cuts, their old age?”

Concern for future implications on his health, however, is not all there is to Leites’ decision.

“I’ve had many fights, so I don’t have the same drive, that same hunger to keep training and competing that I did before,” Leites said. ” I think my time has come. Now, there are new generations coming in. I’m happy for everything I did, everything I went through. I really enjoyed the journey and I’ll keep enjoying it, in a different way.”

The grappling ace isn’t about to give up competition entirely – he’d “go crazy” if he did that, he adds playfully. The idea is to keep competing in jiu-jitsu and submission bouts, in special matches or tournaments, but without the pressure – and impact – of MMA. And professionally, too, the idea is to stay involved in fighting – though Leites keeps an open mind in regard to his outside-the-cage future.

“I have my gym, so I’m going to give it more attention,” Leites said. “I’m going to focus mostly on jiu-jitsu at first, but then I intend to start helping out at Nova Uniao. Then I can have more advanced students that start migrating to MMA. This is something that I think of right now. Things change – not when it comes to my wanting to fight again, but in terms of the field I’m going to act on. I have many things, many life projects, many opportunities.”

Leites comes into his final cage appointment off a rough stretch, riding a two-fight skid that adds up to five losses in his last seven bouts. It’s worth nothing, though, that two of those were to a former UFC champion and a current Bellator champ – Michael Bisping and Gegard Mousasi, respectively – and that his most recent setback stemmed from a heroic effort by Jack Hermansson in a UFC 224 clash that Leites had been shining in.

And he’s had his share of highs, too. Before losing to Bisping, Leites had experienced a notable career resurgence, going on a five-fight winning streak to kick off his second UFC stint. His first one had ended in 2009, not long after the then-one-dimensional fighter lost in a lackluster title bid against then-champion Anderson Silva.

Looking back on his career, Leites does think he could have done more. But then again, isn’t that how everyone feels? “Not everything you plan for possible,” Leites ponders, and just because his path didn’t lead him to a UFC belt, it doesn’t mean that he isn’t proud of it.

“I leave it very satisfied and with my head held high,” Leites said. “Like any athlete, I’ve had highs and lows in MMA. Fighting isn’t simple – you’re meeting someone who prepared just as much as you to be there. Two will go in there to fight and one will leave as the winner. This is an obvious conclusion and you can’t escape that.

“Regardless of not having been champion – the title, the trophy, the belt, the material, that’s for few. Many people have the ability, in my opinion a lot of people have it, but sometimes they miss a fight as they were close to getting there, or you get an injury as you’re about to fight for the belt. So there’s a number of factors that have to come together for a fighter to be a champion. And staying champion for a long time is also very hard, it takes more than just being an exceptional type of person and athlete.”

Leites couldn’t ask for a better send-off from MMA. He gets to do it in the UFC. He gets to do it in his home country. And he gets to do it against a fellow veteran, with a big name, who also happens to be quite tough and “has done a lot for the sport.”

“The only way it could be better is with a win,” Leites said.

As a competitor, Leites says, his mindset is always victory-focused – and that hasn’t changed just because he’s no longer concerned about what that will mean in terms of rankings or title runs. But, at the same time, the Brazilian isn’t putting any added pressure on himself to make that happen just because it’s his final bout, either.

“The win and the loss have the same weight as usual,” Leites said. “I’ve always said in my career, the most important fight is the next one. That’s always how I see it.”

That might have something to do with the fact that, when he looks back on what he’s accomplished as an MMA fighter, it isn’t the outcomes of his bouts that Leites will carry with him.

“The biggest wins, the biggest achievements, for me, is to always reinvent yourself – to fall and continue to get back up, “Leites said. “Because the win is simple. The taste of victory is great for everyone, when it’s all working out. But when you have an injury and you overcome that? When you have surgery and you get over it and win again? Those are the big wins we have in life. What happens in the fight is cool. It’s great, you leave a legacy. But what you also leave to people is how they’re going to look up to you.”

“Legacy” is an intense word and one that’s hard to really gauge. The Brazilian, on his end, has no ambitions of leaving everlasting memories of him. But, if he leaves any impressions behind as he makes his exit from the sport, Leites hopes they are based more on who he is as a person than on what he did in the octagon.

“The thing I find most important, and you can’t measure that because it’s more personal, is for people to see that Thales was a regular guy, like everyone else,” Leites said. “Who has his daily chores, his daily struggles, and who’s up there living a dream. Thank God, I was able to live my dream, to spend part of my life doing what I love to do. And the biggest legacy is for people to see that I was an honest fighter. A simple guy. Someone who fought with heart. That people who have met me know that I’m a cool, simple, humble guy. A guy who’ll talk to anyone, regardless of who they are. That, to me, is the biggest legacy.

“‘Oh, I got there, I knocked 50 people out, I took teeth out of five, all of them combined didn’t last five minutes.’ That doesn’t matter to me. What matters to me are the good things you left people. As a fighter? You have two arms, two legs, you’re fighting there, one can win, the other can lose, that’s it. That’s competition. The thing is how you deal with losing, how you deal with winning, the respect you give your opponent. How you face life. That’s what matters, to me.”

For more on UFC Fight Night 137, check out the UFC Rumors section of the site.