Jeremy Stephens explains why he's been preparing in Mexico for six weeks ahead of his fight vs. Yair Rodriguez. For more UFC, sign up here for ESPN+ http://plus.espn.com/ufc. (1:10)

Jeremy Stephens was living in a large house in Zacatecas, Mexico, with Alliance MMA teammates as he prepared for Saturday's UFC Fight Night main event. And it wasn't cheap.

By the time he enters the Octagon to face Yair Rodriguez in Mexico City, Stephens will have spent six weeks training in Mexico at a cost of around $30,000, more than double what he would have spent if he would have trained at home in San Diego.

Why is he investing approximately 10% of his $300,000 purse to train on the road? Two reasons: It's an extremely important bout as he tries to snap a two-fight losing streak, and secondly, Cain Velasquez.

The last time Yair Rodriguez competed in the Octagon, he flattened "The Korean Zombie" with 1 second remaining in their fight. On Saturday, Rodriguez could be involved in another memorable clash, with hard-hitting veteran Jeremy Stephens opposing him in the UFC Fight Night main event in Mexico City. UFC Fight Night: Rodriguez vs. Stephens

• Saturday, Mexico City

• Prelims: ESPN+, 5 p.m. ET

• Main card: ESPN+, 8 p.m. ET Subscribe to ESPN+ to get exclusive live UFC events, weigh-ins and more; Ariel and the Bad Guy; Dana White's Contender Series; and more exclusive MMA content.

Stephens remembers watching Velasquez fall victim to altitude fatigue in 2015 when he lost his UFC heavyweight title to Fabricio Werdum. "Cardio Cain" became known as "Sea Level Cain" because he struggled with Mexico City's altitude of about 7,382 feet. Stephens doesn't want a sarcastic moniker coined off his inability to deal with altitude, which is why as soon as he agreed to the location of this fight, he knew he would be taking his camp south to train at elevation.

"Cain Velasquez is a cardio machine, as you know," Stephens said. "When he got in there, he looked sloppy. He was definitely taken out [of the fight] within two rounds. He was gassed out. I was like, 'OK, altitude is real.'"

And that reality led to the new training camp in Zacatecas, which sits 8,005 feet above sea level. Stephens' teammates Angela Hill and Jose Quinonez are also on the card and were sharing the house with Stephens. Sijara Eubanks, who fights in Mexico City as well, joined in to help pay expenses.

"Money doesn't really matter to me when it comes down to overall winning and beating someone's ass in their own country," Stephens said, referring to Rodriguez, a Mexico native. "What's that [win] gonna do for me? It's gonna skyrocket my name, skyrocket my career."

Stephens remembers the Velasquez-Werdum fight vividly. It has become something of a case study for UFC fighters.

Velasquez's arms grew heavy. His punches and kicks lacked significant impact. He wasn't able to use his vaunted wrestling and power for a takedown.

Velasquez was breathing heavily. It was like the air had "no substance" to it, Velasquez said.

"The f---ing altitude is what did us -- the altitude," Velasquez's coach Javier Mendez lamented in the immediate aftermath of the June 13, 2015 bout.

Velasquez thought spending two weeks in Mexico City before his fight was enough to acclimate his body. It was not. Werdum, who fought in Mexico City previously, did a month-long camp in the Mexico mountains.

"It was almost like my mind and my body couldn't really make the connection," Velasquez said. "Mentally, I wanted to keep doing stuff ... but my body wasn't cooperating. It didn't have the pop it normally has. It was f---ing like lethargic almost."

Dr. Kevin deWeber, an expert on performance at altitude, said it takes between two to six weeks for the body to acclimatize to high altitudes. There is a lower concentration of oxygen at elevation, and it takes longer for the body to deliver oxygen to cells. He said using hypoxic masks or chambers can be somewhat effective, but they cannot fully simulate living in high-altitude situations and they are not quite an exact science.

Yair Rodriguez, right, is 2-0 in UFC fights in Mexico City, including a win over Charles Rosa on June 13, 2015. Ed Mulholland for ESPN

"Optimally, you're going to want to go two to four weeks early and rest for a few days when you get there," said deWeber, a member of the Association of Ringside Physicians. "Stay hydrated, avoid alcohol, get restorative sleep and begin a gradual training regimen -- one that isn't immediately at full intensity."

Rodriguez spent three weeks in Temoaya, Mexico, which has an elevation of 8,760 feet. When he first arrived, Rodriguez said he was throwing up and was exhausted in between workouts. After a week or so, he could see himself thriving while newcomers were struggling during training.

"I could see the people coming later, I can see the difference between them and I," Rodriguez said. "That's when I could understand the difference between what I'm doing and other people aren't doing. I could feel the difference and I can see it."

Rodriguez fought in Mexico City at UFC 180 and UFC 188, on the undercard of Velasquez-Werdum. For the latter, Rodriguez said he arrived one week early and felt tired in the fight. He didn't want to risk that again.

Mexico City is arguably the most logistically difficult locale on the UFC calendar. The promotion runs shows all over the world, in many time zones and a variety of environments, but nowhere as high as Mexico City.

"When the UFC calls for people to fight in Mexico City, everyone makes excuses," Hill said. "Everyone is like, 'Oh, I'm sick, I'm injured, I don't want to f---ing do it.'"

Angela Hill, left, who is on Saturday's UFC card, said she learned about the difficulties of fighting at altitude when she lost to Tecia Torres in Mexico City in 2015. "I couldn't get any oxygen in me," Hill said. Ed Mulholland for ESPN

Hill lost a listless unanimous decision to Tecia Torres at UFC 188 after gassing out early in the fight. It was a miserable feeling, she said, and she turned down subsequent offers to fight in Mexico City. But her goal in 2019 is to stay active, and she feels like she understands now what it takes to perform there.

"That was the first time that I had to lean on my coach after the fight," Hill said. "I couldn't get any oxygen in me. I felt like my bra was suffocating me. I pulled my sports bra, the elastic, away from my chest for a second and suddenly all the oxygen came into my lungs. It was like, what the f---?"

Stephens opened his training at elevation with Tony Ferguson at his camp in Big Bear Lake, California, before moving to Zacatecas.

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For most events, fighters arrive to fight week on the Tuesday before a Saturday card. In international cities, they will come earlier in an effort to shake the jet lag. Mexico City is the only place where it's crucial to do nearly a full training camp at elevation. That requires uprooting your life, shuttling in coaches and sparring partners and paying more out-of-pocket expenses. It's not an attractive proposition for many fighters.

But for Stephens, it was an investment he needed to make.

"I feel like that's where you get your most learning, when you put yourself in the most uncomfortable places," Stephens said. "This isn't my home, this isn't my bed. The hot water doesn't even work half the f---ing time. I'm in uncomfortable territory, I'm in unfamiliar territory. But honestly, I feel right at home here. I feel great being uncomfortable. I enjoy it."