The headline debate is at holding midfield.
That matters because Mexico’s current balance seems to depend on fluency from deep areas. If Lira starts, Aguirre gets a specialist screener and can keep the centre-back pairing intact rather than moving Álvarez into defence.
Mexico’s other unresolved calls are about profile as much as talent.
Further forward, Julián Quiñones and Alexis Vega seem to be competing for the left-sided attacking role. One offers direct running and physicality, the other more combination play and craft between the lines. Tournament football often turns on that kind of stylistic choice.
Reports suggest Aguirre has found something with Lira, Álvaro Fidalgo and Brian Gutiérrez. Fidalgo appears to be setting tempo from deeper positions, while Gutiérrez has emerged as a freer runner who can connect midfield to attack. That shape looks hard to break up on the eve of a major opener.
The next clue will come when the team sheet drops for South Africa. Mexico seem close to a settled side, but the calls around Álvarez, right-back and the left flank could define not only the opener, but the direction of their whole group-stage campaign.