The sweltering Dallas heat will provide the backdrop, but the real temperature will rise when Portugal face an in-form Spain in one of the most eagerly awaited World Cup last-16 clashes tonight. Touted as the tournament favourites and among the most complete teams in the competition, Spain have been flawless defensively and will once again look to teenage sensation Lamine Yamal to provide the spark. Portugal, meanwhile, will rely on collective resilience while hoping their legendary captain, Cristiano Ronaldo, can once again deliver on the biggest stage.

** Spain are yet to concede a goal in this year's tournament, keeping clean sheets in their opening four matches of a World Cup campaign for the first time. They are only the second European nation to achieve the feat, after Switzerland in 2006.

** Having also kept Morocco scoreless before their penalty-shootout exit in the round of 16 in 2022, Spain could become the first team in World Cup history to keep six consecutive clean sheets if they shut out Portugal.

** La Roja are unbeaten in their last 34 matches (W25 D9), one shy of equalling their longest-ever unbeaten run of 35, set between February 2007 and June 2009.

** Much of that success has come under coach Luis de la Fuente, who is unbeaten across his first 11 matches at either the World Cup or Euros (W10 D1), conceding just four goals.

** Portugal have won just one of their 12 competitive meetings with Spain (D6 L5) – a 1-0 victory in the group stage of Euro 2004.

** However, there has been little to separate the Iberian rivals at major tournaments, with each side winning once and the other three of their five meetings ending in draws.

** Portugal will take confidence from defeating Spain on penalties in their most recent meeting, in the UEFA Nations League final in June 2025.

** Portugal will be looking to reach the World Cup quarterfinals for the fourth time, and for the first time in consecutive tournaments.

** However, they have not won successive World Cup knockout matches since 2006, when they defeated the Netherlands and England before eventually losing to France in the semifinals.

** If Portugal are to end Spain's unbeaten run, coach Roberto Martinez will need Ronaldo at his clinical best. The Portugal captain has scored four goals against Spain -- the joint-most by any player against La Roja, alongside Eduardo Vargas.

** Spain, though, have their own in-form forward in Mikel Oyarzabal. His four goals at this year's World Cup are already the most by a Spain player in a single edition since David Villa scored five in 2010, when La Roja lifted their maiden World Cup trophy.