Late last March, the Padres and Astros played two spring training tune-ups at Estadio Fray Nano in Mexico City, home field of the Diablos Rojos del México of the Triple-A Mexican League. Both teams sent split squads, leaving several starters in the states, but some of their stars (including Carlos Correa and José Altuve) made the trip.

In the first game, Astros starter Chris Devenski — who would go on to record the American League’s best park-adjusted FIP during the regular season among pitchers with at least 100 innings pitched — combined with a bullpen that would go on to be MLB’s best to limit the Padres to one run, while the Astros beat up on the Padres’ pen for an 11–1 win. The next day, things were different. In the bottom of the first, three Padres took the Astros’ Brady Rodgers deep, putting the Pads up 8–0. Eight innings (and two additional San Diego dingers) later, the final score stood at 21–6.

The Padres, remember, had the second-worst offense in baseball last season — third worst, if you’re charitable and exclude pitcher hitting. Over the rest of the season (exhibitions included), they never topped 17 runs in a single game. In this game, though, they posted a score that would have won in blackjack. And in the two Mexico City contests combined, the Astros and Padres combined for 39 runs and eight homers.

Yes, it’s a small sample, and yes, many minor leaguers were involved. But that slugfest of a series may have been a fairly representative preview of what MLB games in Mexico City would look like, which could be cause for concern as momentum builds behind Mexico City as a permanent major league city.

At the All-Star Game FanFest last week, MLB commissioner Rob Manfred mentioned Mexico City (along with Montreal and Charlotte) as possible long-term recipients of an expansion team, just as he had the previous spring (when he announced plans to open a Mexico City office and identified Mexico City and Montreal as “personal [front-runners]”), as well as in October 2015, when he visited Mexico and talked up its potential as a new location for the league. Manfred’s latest spoken overture to Mexico City comes on the heels of a report from earlier this month — since confirmed by executive director of the MLB Players Association Tony Clark — that the Padres and Dodgers could play a regular-season series at Estadio Fray Nano next April, which Manfred has mentioned as a crucial step on the path to a more regular presence.

Mexico City makes sense as a site for a few reasons, so it’s only logical for Manfred to keep the option alive. First, it’s enormous, with the largest metropolitan population (roughly 21 million) of any North American city, with the possible exception (according to some sources) of New York. Second, it’s a largely untapped market. As Manfred told Jayson Stark in an ESPN story last year, “a team in Mexico opens up the Mexican television market, which is significant in ways that are much broader than the arrangements that we have there now.” He also noted that a team based in Mexico would “help us improve the flow of Mexican players into Major League Baseball,” which would in turn “help us in the Hispanic market in the United States.” (Only 13 Mexican-born players have appeared in the majors this season.) And with the closest MLB team roughly 1,000 miles from Mexico City, no major league owners would be up in arms about a new club cutting into their share of local attendance.

The downsides are equally obvious, though. That great distance from the nearest MLB teams would also mean more travel. Safety would be a concern: Although the city’s official crime and murder rates aren’t out of line with domestic tallies, that could be due to rampant underreporting, and violence across Mexico (including suburbs of Mexico City) has made 2017 one of the country’s deadliest years since the peak of the government’s crackdown against the cartels. Whatever the true figures, the perception of danger could hurt a Mexico City franchise’s chances of persuading players to move south.

“The safety aspect I don’t think could be guaranteed,” says former major league pitcher Todd Coffey, who played for the Diablos Rojos for part of 2015 before, he tells me via phone, he and the team mutually decided to part ways. “And I think that would play a big mind in having your family there. Put it this way, when I played, I didn’t bring my kids, at all. I wouldn’t do it. … That would be, I think, the biggest hurdle, that I don’t see [Manfred] being able to convince the union and players that it’s a good thing.” Coffey also cites the language barrier as a disincentive for U.S. players, saying that his time in Mexico City turned the tables and gave him “a culture splash of what the Dominican players feel like when they first come over to the states and play ball.”

What’s more, although Mexico City is packed with potential ticket buyers, the route to financial success for a new team might not be as smooth as it seems. Baseball ranks behind soccer and boxing in popularity among Mexico City sports, and the Diablos Rojos, who were founded in 1940, have already earned the loyalty of local fans, who would have to divide their attention between an MLB franchise and the 16-team Mexican League, which is predominantly populated by Mexican players.

“The atmosphere for baseball is big, but I think it’s more big because it’s the local teams,” Coffey says. “I think they enjoy baseball, but I think the fact that there’s very [few] Mexican players that are in the major leagues … would definitely do a disservice for [Manfred’s] idea of expanding down there for baseball.” And while the city proper is wealthy compared with many American cities, the metro area is comparatively poor, an income inequality that could curtail the team’s effective fan base.

Compared with those problems, concerns about altitude might seem easy to surmount. From a statistical perspective, though, nothing makes Mexico City more fascinating — and, for anyone who believes that baseball is already overly reliant on dingers, potentially problematic — than the thin air that helped power the Padres’ 21-run salute. Mexico City sits 7,380 feet above sea level, more than 2,000 feet higher than Denver. If you think Coors Field inflates offense or that the league’s current record home run rate is high, the addition of a Mexico City franchise would force another recalibration of your baseball beliefs.

Physics of baseball expert Alan Nathan estimates via email that the air density in Mexico City is only 76 percent relative to sea level, compared with 82 percent at Coors. According to Nathan’s calculations — holding all else equal except altitude — a “standard long fly ball” with a 103 mph exit speed and a 27.5 degree launch angle would travel 398 feet at sea level. At Coors, it would fly 427 feet. And in Mexico City, it would cover 438 feet. “The balls fly,” Coffey confirms. “It would be the highest home run ballpark ever.”

Tadeo Varela, a statistical analyst for the Toros De Tijuana — who, like the Diablos Rojos, play in the North Division of the Mexican League — sent me the Diablos Rojos’ home/road slash lines from 2015–17, the three seasons that the team has spent at Estadio Fray Nano. Despite the symmetrical park’s wide expanses of foul territory and reasonable fence distances (325 feet to left and right, 410 to center), the Diablos Rojos have hit far better at home.

According to Varela, the team averaged 6.26 runs per game at home and 4.53 runs per game on the road over those three years, for a park factor of 1.38 (that is, the park increased scoring by 38 percent). Brian Cartwright, the creator of the Oliver projection system, sent me his three-year factors for Fray Nano relative to the rest of the Mexican League, which tell a similar story, including a 1.41 factor for home runs and a 1.29 factor for singles. One could, of course, build a ballpark with more distant fences to suppress homers, but that would only invite more balls to fall in front of outfielders.

To make matters worse, Fray Nano decreases strikeouts (.88 park factor), probably due to decreased pitch movement in the city’s thin air. Through some combination of altered movement and flat-out fear of throwing strikes, it also tends to supply more free runners who can come around to score on the inevitable home runs, posting park factors of 1.11 for walks and 1.25 for hit by pitches. These combined effects force pitchers to shy away from their strengths. “I had to do different pitches for sure,” Coffey says. “The sliders didn’t break as hard, so it’s more like a cutter. And then your sinker doesn’t sink as much, so you throw more four-seamers, which is what makes the home runs happen a lot more.”

Here’s the frightening part. All of those park factors are relative to the league — and the league itself inflates offense. The Mexican League includes six parks at elevations higher than 3,000 feet, most of them higher than 5,000 feet. That means that many of the road parks to which we’re comparing Fray Nano are themselves launching pads, which makes Fray Nano’s effect appear more modest. Sabermetrician Mitchel Lichtman estimates that the Mexican League, relative to MLB, has a league factor of approximately 1.09. Multiply Fray Nano’s 1.38 park factor for runs scored by that 1.09 league factor, and you get 1.50 — Lichtman’s best guess as to what its park effect would be in MLB. By comparison, he estimates the park factor of Coors Field as between 1.30 and 1.40.

Nor can a humidor help, as it has at Coors and in Colorado Springs (where the Brewers’ Triple-A affiliate plays), and as it would in Chase Field, where the Diamondbacks hope to install one next season. The air in those environments is dry enough that a humidor set to 50 percent relative humidity has a significant effect on the ball. In Mexico City, the relative humidity during the summer months is considerably higher than 50 percent, so if a team were to store baseballs in the same conditions that the Rockies do at Coors, the balls would dry out and fly farther. Nor could a Mexico City team keep cranking up the humidor to, say, 90 percent or higher in a bid to dampen the baseball. “A standard MLB baseball stored at 100 percent [relative humidity], 70 [degrees] absorbs enough water to increase the weight to 5.6 oz., which is way outside the allowed range [of 5.0 –5.25 oz.],” Nathan says. “A humidor could not be used to mitigate somewhat the elevation effect, as was done at Coors, without increasing the weight an unacceptable amount.”

On top of everything else, playing at altitude saps pitchers’ endurance. “You’d see pitchers not pitch deep into games at all, because you just can’t,” says Coffey, who ran with an altitude mask at home when he was preparing to pitch in Mexico City but nonetheless tells me it took “literally a month just to where I could feel like I was catching my breath. But the moment you get back into it, like a quick play, a bunt or something, takes a little bit longer again to catch your breath.” Granted, Coffey’s physique in the latter stages of his career didn’t make him look like a model of conditioning, but he says the altitude hit the whole staff hard. “I’ve seen pitchers down there who are in unbelievable shape, as soon as around the fifth inning hits, they’re tired,” he says. “And it wasn’t lack of ability, they’re just gasping for air.”

Although the Diablos Rojos have hovered around .500 this year and last, they’ve had great success in the long run, winning 16 Mexican League championships. For decades, though, the dominant narrative around the Rockies has been whether and how they could compete in their park, to the point that the team has considered desperate solutions such as a pressurized dome and a clubhouse that doubles as a hyperbaric chamber — and now MLB is eyeing an environment that dwarfs Denver’s offense-inflating traits. Any institutional challenge that the Rockies have faced — including attracting, developing, and preserving pitchers, and a possible offensive hangover effect on the road — should in theory be exacerbated by the altitude of Mexico City. Coffey, who got into seven games in Coors Field, concurs. “Mexico City was tougher,” he says. “It was. … Fastballs are going to go where they go, but it’s the breaking balls you can’t get the snap on. But by the time you’re leaving Coors, you feel better, and you have that snap on the ball. Down there, I could never get the feel to it at all.” Coffey also claims that Mexico City’s specter can linger after you’ve left. “If you start tinkering with stuff when you go, now you go to another city where it’s ‘normal,’ and then you have to retinker it back.”

Manfred’s instinct to expand beyond the borders of baseball’s homeland is a wise one, as interest in the NBA and NFL grows across the globe and MLB’s built-in audience ages. Mexico’s proximity compared with other baseball-playing countries makes it an alluring location, and Mexico City’s size has obvious appeal. But baseball in Mexico City would make the extreme version of the sport we’ve watched in a mile-high stadium seem tame. That doesn’t mean that expansion somewhere in Mexico wouldn’t work. But a slightly lower location might make for a more comfortable home.