It was earmarked as a major potential obstacle for England this summer: a last-16 showdown with Mexico at the legendary Azteca.And now it’s a very real obstacle, after both sides topped their respective groups and progressed from their round of 32 ties.Harry Kane scored both goals as England beat DR Congo to set up a last-16 clash with MexicoGettyHow many Wembleys?!England will have to beat the co-hosts at their iconic home in the early hours of Monday morning – live on talkSPORT – if they’re to take a step closer to World Cup glory.The statistic that Mexico have lost only two out of 89 competitive games at the Azteca since it opened in 1966 has been widely circulated.Likewise, much has understandably been made of the altitude this great cathedral of football sits at: a dizzying 7,220ft (around 2,240m) above sea level.To put that into some context, you’d have to stack 50 Wembleys on top of each other to get to the same height.The Azteca is also more than twice as far above sea level as the highest point in England, Scafell Pike in the Lake District.It’s bound to take its toll on England’s players, but altitude isn’t the only factor in Mexico’s success at the now 87,000-seater arena where Pele and Diego Maradona both lifted the World Cup – and where the latter broke English hearts in captaining Argentina to success in 1986.Context is keyIt’s important to look at the general quality of opposition Mexico have generally faced at the Azteca.The fact that El Tri have qualified for nine of the last ten World Cups they haven’t hosted (they were disqualified from the 1990 tournament after fielding overage players in a U20 tournament) speaks to their status as big-hitters in the CONCACAF region.Generally, they are one of, if not the strongest side in their confederation.For instance, in qualifying for the 2022 World Cup, Mexico faced the following sides at the Azteca: Jamaica, Canada, Honduras, Costa Rica, Panama, the USA and El Salvador.Maradona scored two of the most famous goals of all time against England at the Azteca in the quarter-finals of the 1986 World Cup, including the infamous ‘Hand of God’Bob Thomas Sports Photography - GettyMexico made it four clean sheets in four games at this World Cup by beating Ecuador 2-0 in the round of 32GettyMexico are currently ranked higher than all of those nations by FIFA – they climbed to tenth when the most recent rankings were published on the eve of this World Cup – with all of them bar Canada and the USA more than 30 places below them.Granted, El Tri haven’t lost at the Azteca since a 2-1 World Cup qualifying defeat to Honduras in 2013 and their only other competitive defeat in the stadium’s 60-year history was against Costa Rica in 2001. But the only team they’ve faced between then and now who most would consider to be in world football’s top echelon is Portugal, with whom they drew 0-0 this March.It should be noted that Portugal were by no means at full strength that day, with Vitinha and Pedro Neto among those that didn’t start while Cristiano Ronaldo and Ruben Dias weren’t involved at all.And while they are virtually flawless in games that matter, Mexico have lost six exhibition matches at the Azteca since 1966, losing friendlies to Hungary, Brazil, Italy, Peru, Chile, and Spain.The Mexicans have punched above their weight to beat the world’s best at the Azteca, though. Mexico's Azteca record at the World CupMexico 0-0 Soviet Union (1970)Mexico 4-0 El Salvador (1970)Mexico 1-0 Belgium (1970)Mexico 2-1 Belgium (1986)Mexico 1-1 Paraguay (1986)Mexico 1-0 Iraq (1986)Mexico 2-0 Bulgaria (1986)Mexico 2-0 South Africa (2026)Mexico 3-0 Czechia (2026)Mexico 2-0 Ecuador (2026)A star-studded Brazil team, ranked No.1 in the world, lost there twice: in the 1999 FIFA Confederations Cup final and in a 2003 friendly.England to provide Mexico’s first true test?Throw it forward to the ongoing tournament and Mexico have been impressive – along with Spain, they’re one of the only teams left standing who’ve yet to concede a goal – but again, the quality of opposition has generally been inferior.El Tri’s group looked favourable when the group was made – and so it proved as they made light work of South Africa, South Korea and Czechia, the latter two of whom have seen their managers resign following abysmal early exits.Mexico went on to dispatch a defensively stubborn Ecuador side 2-0 in the round of 32, but England still ought to test them more than anyone they’ve encountered at the Azteca in some time.Everything stacked against EnglandSport at altitude is always a challenge, but England, who have an awful record in these conditions, will have it worse than most.The Three Lions only have two days to acclimatise to the altitude after travelling to Mexico City on Friday, having beaten DR Congo on Wednesday. Tuchel has already said it is ‘impossible’ for England to adjust in timeGettyJames Barber from the Altitude Centre gave the talkSPORT Breakfast Show offered his expertise on the challenge facing England.“It’s really tough,” he said. “And it’s not necessarily that one single sprint will feel harder, but it’s the fact that you have to do that time and again. “You have to sprint, recover very quickly, and sprint again. And across the course of 90 minutes, that just accumulates, that fatigue. “Every single recovery is a little bit impaired, and it’s going to mount up from there across the course of the time they’re playing. “The altitude sickness thing is tough – and they’re dealing with that. We’re talking about match day, but they’re going to be up there for a couple of days beforehand as well. “What that does to the recovery from their last match, from the travel, all the rest of it… it’s a challenge right from the off.”Altitude sickness becomes a factor at more than 2,000m above sea levelGettyThis might not be such a problem if it was the same playing field for both teams, but Mexico have a distinct advantage.Barber added: “It’s likely to still affect them compared to being at sea level. But probably not quite to the same level. “They spend a lot of time up there over the course of the competition. Some of them live out there. They’ll be out there full-time. “Some of them will have been born at altitude, which might protect them as well a little bit.” To make matters worse, Mexico have had an extra 13 hours’ rest, with no travel requirements. Barber added: “The other thing as well, we’re talking about the physiology, but there’ll be things like the flight of the ball will be different at altitude.“Because the air is thinner. So there’s less air resistance. So if you kick the ball with the same power, it’ll travel further than it would at sea level. The ball will swerve slightly differently, all that sort of thing.“So there might be little factors like that, but they’re just a little bit more used to it than the England players will be.”World Cup WhatsAppDon't miss an update from talkSPORT in our dedicated World Cup WhatsApp channel.Search for ‘talkSPORT World Cup’ in your ‘Updates’ tab on WhatsApp and we’ll drop the proper, unfiltered football chat straight to your lock screen—no fluff, just pure talkSPORT energy.It’s where you’ll find out all the new rules to watch out for, England and Scotland reaction and big match player ratings. Plus there will be loads of debates on the biggest talking points as Haaland, Mbappe, Kane and the biggest names in football descend on America, Canada and Mexico.