England have overcome several World Cup obstacles already this summer – yet Thomas Tuchel is fully aware of the seismic challenge that awaits at the cauldron that is the Azteca Stadium in the last-16.
The co-hosts have been whipped up into a piping-hot frenzy over the last three weeks, unleashed most impressively in their last-32 victory against Ecuador. Following a weather delay, the rampant Julian Quinonez and Raul Jimenez landed a pair of haymakers to leave their South American opponents dazed.
Yet England's most daunting task on Sunday night could well be the conditions, with altitude set to be a great leveller with Mexico City's iconic Azteca situated 7,220ft (2,240m) above sea level.
With the air thinner and less oxygen available to replenish the bloodstream with each sharp intake of breath, those lung-busting recovery runs become more excruciating at each turnover.
"There will be a lot of obstacles awaiting us," said England boss Tuchel, after his side's 2-1 win over DR Congo. "The altitude will be a big disadvantage, of course, because we cannot adapt to it in four days – it's just impossible.