Editor's note: This story originally ran ahead of a UFC Fight Night main event bout between Justin Gaethje and Edson Barboza in March. Gaethje won the fight via first-round TKO.

Rafaello Oliveira could not continue. Midway through the second round of his fight with Edson Barboza in 2013, he had taken 23 strikes to his left leg. His body crumpled to the mat on the final shot, forcing referee Herb Dean to end the bout early.

"That is one of the nastiest visions of damage from leg kicks that I can remember in a long time," UFC commentator Joe Rogan said on the broadcast. "That kid is a monster."

Oliveira was transported to a hospital after the matchup and was given morphine -- twice -- to help with his injury.

"I could barely walk [that night]," Oliveira remembers six years later. "It was the hardest pain I ever felt as a fighter after a fight."

Barboza's 257 leg kicks in his UFC career are tied for seventh most in history of the promotion. He has four wins by kicks and has a 78 percent leg-kick accuracy.

Justin Gaethje, whom Barboza faces in the main event of UFC Fight Night in Philadelphia on Saturday, is similarly potent. Of his landed significant strikes, 36 percent are to the legs. He has connected on 125 leg kicks in his four-fight UFC career, the most by any fighter over that span.

ESPN spoke with four fighters who have faced Barboza or Gaethje about what it feels like to deal with these lethal leg kicks. Here is what they recall from those nights, in their own words.

Lost to Edson Barboza by unanimous decision on July 23, 2016

Barboza is the full package when it comes to leg kicks. You got people who are fast at leg kicks but don't have as much power. Or they have powerful leg kicks but are a little bit slow. Barboza is both of them. He's extremely fast, powerful and not to mention tactical with it.

Usually in a fight, things don't hurt because your adrenaline is up. But after he chops your leg so much, you start to feel it. You start to feel the bruising. And then it goes so deep past the bruising that it gets to the nerve. Then, when it gets to the nerve, your leg just stops reacting as well as you'd like it to. You can't put as much weight on it. You're not moving as well, and it's just out of your control.

"If someone gave me $1,000 to take another leg kick from Edson Barboza, I would be like, 'I'm good.'" UFC fighter Gilbert Melendez

It's not like a knockout punch. It's like chopping down a tree. You start timbering over. You can only take so many. I didn't go down after the first leg kick, but then another one came. You take it well, but then all of a sudden seven have landed and then you start realizing, "I'm taking too many." Somewhere in the second round, my leg just started giving out after the 12th or 13th one hard on the money.

People are going to tell you, "Hey, how come you didn't check that kick?" I said, "Listen, I've fought many great strikers, and it's a lot easier to check and a lot easier to handle." You try to go fight Edson Barboza and stop that leg kick. "Why don't you just slip that punch?" Of course, it's easier to slip that punch, but go slip Floyd Mayweather's punch. That's a different story.

Adrenaline, though, is a huge tool. While your adrenaline is up, you can absorb a little bit more. A leg kick from someone like Edson Barboza is taking a bat to your leg. Imagine a hard, bony shin from a beast of a man just going right into your thigh and hitting that nerve. That's no good. It's like taking a wooden bat to your thigh. That's what it feels like.

If someone gave me $1,000 to take another leg kick from Edson Barboza, I would be like, "I'm good." If they offered you $10,000, I would suggest you not take it. Your knee surgery would cost more.

Lost to Edson Barboza by TKO (leg kicks) on July 6, 2013

The game plan was to pressure and keep going straight forward like boxing to try and close the distance, then take it to the ground. I wasn't able to follow the game plan. Now more experienced, I think it was the biggest mistake in my whole career. I was like, "The guy is a striker, so let's strike." I had a tough mentality, but it was really stupid.

As soon as we started, he threw a kick on my ribs. That was good, precise striking that hurt a little. It's like a Mike Tyson punch in the first. Everything changed.

play 1:06 Barboza finishes fights with leg kicks Edson Barboza puts his kicking prowess on full display with these wins over Rafaello Oliveira and Gilbert Melendez.

His speed is different from anyone I've ever trained with in my life. I'm around a lot of high-level guys, but his kick speed was hard to deal with it. I couldn't, really. I don't think I defended any kick from him. It was too fast. And then over and over in the same spot. You can take it for the first two, three or four, but after that? Your body can't take it. Everything is just so painful. In all of my fights, that is what hurt the most -- those leg kicks.

You have a physical pain first. After going over and over, it's not a physical pain but a mental one right now. You just feel really weak. You cannot do anything. Your leg is so heavy, you can't defend. You're just dealing with so much pain over and over. It's hard to stay on your feet.

It's not even the pain but the pride. After you do so much preparation and give 100 percent, and then not [be] able to get the job done? It really hurt. The pain is just momentary. But inside, it hurts your spirit and ego. You feel like s---, really.

The pain is more inside. You know you were defeated by another human being in an equal battle and you could not do anything about it.

Lost to Justin Gaethje by TKO (leg kicks) on June 14, 2013

Going in there against someone like Justin, whose sole purpose is to dismantle you, attacking something that is one of the weakest parts of your body, is probably not going to work out real well. You're not going to get a workout partner who is going to throw it like he throws it. You're never going to be able to prepare for it until you're actually in there with him.

It's one of those things where he just gets you off of your rhythm. Your timing gets off because he does it differently than other people. He is relentless with it. He keeps throwing the kicks. Because he has great kicks and they are disguised, you have to be aware of it.

"You're not going to get a workout partner who is going to throw it like he throws it. You're never going to be able to prepare for it until you're actually in there with him." Former WSOF fighter Brian Cobb

His kicks are so masked. You can't read his hips because he throws it so cleanly and masks it well with good feints. He's also constantly coming forward so it's not like, "Hey, he's throwing a kick, so I should check that." It's, "He just threw a kick. Damn."

It's hard to read. He constantly comes forward. He's constantly in your face. You're trying to deal with maybe cutting off the cage from him, taking angles away and things like that. You wind up stepping into things and doing exactly what he wants. I remember my coaches in the corner after the first round said, "You gotta check the kick." I knew I needed to. But it was just really hard to see coming.

He threw a kick as I was coming in for a jab. I felt my leg -- I wouldn't say pop, but I would say buckle. I went to back up, and there was nothing there. I didn't have the support I needed. A lot of people thought I was trying to say, "Timeout," but I was basically giving the "cut it" symbol with my hand. I was like, "I'm done." [Steve Mazzagatti] was the official and kind of stared at me. I was like, "Hey, idiot, I'm tapping on my chest." Justin came in and landed a couple shots and I literally couldn't stand on my left leg. I put my back against the cage and slid down to my butt.

I tore my LCL, MCL and my meniscus in that fight. It's hard to say [whether it was all because of Justin]. I did damage to my right knee before the Johnny Nunez fight. I have no idea, but he was definitely the contributing factor in what put me over the edge. That is for sure.

Defeated Justin Gaethje by TKO (punches) on April 14, 2018

He has reckless abandonment for his own health, for his own limbs, for his body positioning to receive punches after he kicks. He just acts like he's kicking a soccer ball.

Normally you have to set things up, worry about what's after the kick. All he focuses on is just the leg connecting. He doesn't care about what's before or what's after or what position he's in to receive or to make you miss, to receive damage or to give it. He doesn't have step two, three. He just has step one, and that's all he's focused on -- and step one is smash.

play 0:47 Gaethje's leg kicks can change a fight Look at the damage Justin Gaethje inflicted to the front leg of Dustin Poirier during their bout last April.

He doesn't care about what's next. He doesn't care about keeping himself safe. Most fighters try to protect themselves or try to set their kicks up with punches or try to get out of the way after. Because you do that, you put 80 percent or you put 50 percent on the kicks or you can have a Plan B after your kick lands. He's only focused on landing that kick and it's 100 percent every time.

My quad is partially torn because of him. I had to do a lot of physical therapy. I didn't know it in the fight, but I knew it the night of and the next morning. He tore my quad. I'm trying to think of another time I've been seriously damaged with kicks. Jim Miller hurt my calf really good, but nothing like that.