There is a particular irony awaiting England at 2,200 metres above sea level. Throughout this World Cup - against Ghana's disciplined retreating lines, against DR Congo's stubborn, narrow banks - the low block has been England's torment. What has frustrated them most, the shape they have laboured against and occasionally despaired of breaking, is now, in all likelihood, their best hope of survival.
The Azteca does not simply ask questions of a team's quality. It asks questions of their lungs, their legs and their willingness to be honest about what they are. At this altitude, there is significantly less oxygen available with every breath. The body's capacity for high-intensity running - the relentless press, the surging overlaps, the repeated sprints that define Tuchel's best-case England - diminishes measurably, often dramatically, somewhere around the hour mark. Players who have not acclimatised properly do not simply tire. Their muscles seize.
Mexico understand this intimately. They have lost twice at the Azteca in 89 competitive matches. Twice. The altitude is not incidental to that record. It is foundational to it.
And so England arrive at the most iconic stadium in the Americas carrying a peculiar tactical instruction: be the thing they have spent three weeks trying to defeat. Defend deep. Compress space. Conserve energy. Invite Mexico onto them and wait, patiently and without panic, for the moment the game opens.
It is not a romantic strategy. It rarely produces the kind of football that generates highlight reels or newspaper column inches. But knockout football at altitude is not a romantic business. It is a physiological negotiation, a slow accumulation of small advantages, an exercise in deciding which risks are worth taking and precisely when.
Harry Kane will drop deep. Jude Bellingham will pick his moments rather than dominate them. Bukayo Saka will hold his width without the relentless energy that makes him exceptional at sea level. England will, in short, ration themselves, storing what they cannot afford to spend until the game demands it.
The group stage has demonstrated, sometimes uncomfortably, that England can play this way. What remains to be seen is whether they can do it with the discipline, the collective trust and the quiet conviction that a knockout match at altitude against a side that has never lost here at a World Cup genuinely requires.
The Azteca has been making visiting teams feel ordinary since 1970. England return for the first time since 1986, when Diego Maradona made history in a World Cup quarter-final. In the early hours of Monday, England will need to make a very different kind of history.