Thomas Tuchel cut through a surreal pre-match press conference with a wry smile and a blunt dismissal after reports swirled that England’s medical team had explored the use of Viagra to counter the high altitude. “The information and support did not reach me — that is not true,” the manager said, sitting beside midfielder Jordan Henderson, who deadpanned his own aside: “Well, the Viagra helps … I’m joking.” The exchange, hours before their World Cup round-of-16 match against Mexico, distilled an odd subplot into a moment of gallows humour.

The pharmaceutical rumour was rooted in genuine physiology. Sildenafil, the active ingredient in Viagra, acts as a pulmonary vasodilator that could theoretically ease oxygen uptake in thin air. Since the World Anti-Doping Agency does not prohibit it, speculation gained traction in British and Indian media that the squad might be offered the drug. Italian news coverage, however, cited WADA-commissioned studies suggesting any advantage would likely occur only at elevations above 4,000 metres — well beyond the 2,240 metres of the Estadio Azteca — making such a benefit improbable for the Three Lions at this venue.

If science offers no edge, local history certainly hands one to Mexico. The Azteca has witnessed only two home defeats in 89 matches, none since 2013, and the co-hosts swept their group with four straight wins. England, by contrast, had to scramble past DR Congo in the round of 32 with two late Harry Kane goals. Mexican media have framed altitude as the team’s natural ally, and the visiting side’s physical adaptation — or lack of it — dominated the tactical narrative in the buildup. Tuchel acknowledged he suffered a mild headache and disrupted sleep himself, while players reported feeling the strain in the first minutes of training before gradually acclimatising.

Off the pitch, the hostility has been more visceral. Mexican supporters, deploying the same guerrilla tactic used against Ecuador earlier in the tournament, located England’s hotel and subjected the squad to nights of car horns, chants and firecrackers. British reports detail a police cordon thrown around the perimeter after the FA’s security team intervened, a move aimed at securing rest in the hours before kick-off. “We feel it even when we’re not training,” Tuchel said of the altitude, conceding that full physiological adaptation was impossible in the short window.

With a quarter-final place at stake, England face a dual test of lungs and nerve against a partisan crowd and a punishing climate. The Azteca’s thin air, home invincibility and a sleep-deprived buildup leave Tuchel’s men confronting a knockout contest shaped as much by geography as by football.