England Arrives at Mexico City Hotel Under Riot Police Guard. The Azteca Awaits Sunday at 6 p.m. Local.

Since FIFA's kickoff reversal was resolved in the early hours of Saturday, England's focus has shifted entirely to what happens Sunday evening at the Estadio Azteca.

The scene outside England's hotel in Mexico City's Santa Fe district has been what you'd expect. According to The Guardian, more than 100 riot police in bullet-proof vests are stationed outside, with a police dog and drone deployed nearby. When England's team coach arrived Friday, hundreds of fans were waiting, many booing and chanting "Mexico." Mexico's National Guard lined the hotel entrance.

The security escalation isn't theater. Four people died during celebrations following Mexico's round-of-32 win over Ecuador, and Ecuador's football federation formally complained to FIFA after local fans used loudspeakers, horns, and motorcycles to deliberately disrupt the Ecuadorian players' sleep the night before that match. Mexico won that game 2-0. England, aware of the playbook, reportedly tried to keep their hotel location secret. It didn't work.

England midfielder Morgan Rogers told BBC Sport: "I won't be happy if it wakes me up. We'll deal with it as best as possible. It's just another obstacle to overcome but we're ready."

To guard against sleep disruption, BBC reports players are being offered natural sleep remedies and white noise machines. Some will bring their own earplugs.

Mexico has lost twice in 89 competitive matches at the Azteca, winning 70 and drawing 17, according to The Guardian. They are unbeaten in 10 World Cup matches at the stadium. They have not conceded a goal in this tournament, making them one of only two teams, alongside Spain, to hold a clean sheet through the group stage and into the round of 16.

The stadium sits at 2,240 metres above sea level. Al Jazeera cited sports medicine experts who note that thinner air at altitude reduces oxygen availability, accelerating fatigue and making repeated sprints harder for players not acclimatised. England's players are not acclimatised. Manager Thomas Tuchel acknowledged to The Guardian this week that the FIFA-mandated travel window leaves no good option: "The recommendation is you either go 10 days before, which is too long for us, or last minute, which is not allowed by FIFA."

Mexico, by contrast, has played three of four World Cup matches at the Azteca this tournament and trains and lives at altitude.

The crowd and the altitude are real headwinds. The opposition's record, examined closely, is less frightening.

The Guardian ran Opta data on the playing styles of each team's group-stage opponents. Mexico's wins came against South Africa (60th in FIFA rankings), South Korea (whose president publicly called for an investigation into the national team's performance), and Czechia (a side that lost to the Faroe Islands in qualifying). Ecuador, who Mexico beat 2-0 in the round of 32, scored only 14 goals in 18 World Cup qualifying matches.

Mexico played slow football against slow teams. The Opta metrics show South Korea had the lowest direct speed of all 48 World Cup teams, with South Africa and Mexico also in the bottom seven. England's opponents, meanwhile, have ranked among the faster-moving sides in the tournament. England has simply not been stress-tested by the kind of pace it will bring itself.

Mexico did hold Portugal to a 0-0 friendly at the Azteca earlier this year, but as The Guardian notes, friendlies against a resting European side are a different exercise than a World Cup knockout match against a team built around pace.

Former England striker Alan Shearer, writing for BBC Sport, made the fair point that the hostile environment is also, from a player's perspective, the whole point. "These are the kind of games and moments you train and work so hard for all your life," Shearer wrote. "I've wanted to go to the Azteca since I watched the 1986 World Cup on TV as a teenager."

The crowd will be roughly 80% Mexican, according to Shearer's estimate, in a stadium with a capacity of 87,000. Over 3,000 England fans are expected in attendance, according to BBC Sport.

The strongest counter-argument to England's optimism is a legitimate one: England players have spent their entire careers at sea level in the Premier League. No amount of tactical preparation fully replicates the physical reality of running at 2,240 metres against a team that trains there. If the match goes to extra time, the altitude disadvantage compounds directly.

Tuchel has not disclosed his lineup or how he plans to manage England's energy budget over 90 minutes in thin air. That tactical decision, specifically how aggressively England presses in the first half versus conserving legs for the second, may be the actual determining factor Sunday night.

The match is scheduled for 6 p.m. local time (1 a.m. Monday BST). UK pubs have been granted extended licenses until 5 a.m. by Prime Minister Sir Keir Starmer. Whether England's squad slept Saturday night is a question that won't be answered publicly until after the final whistle.