Spain did not need Mikel Merino's 89th-minute header to prove they are the best team at this World Cup. They needed it to prove they could win a game that had, for 88 minutes, refused to yield to their superiority. The 1-0 victory over Portugal in the round of sixteen was a study in controlled dominance meeting stubborn resistance — and then, finally, a moment of vertical brilliance to shatter the stalemate.

Merino's goal was the kind that looks inevitable in replay and impossible in real time. Dani Olmo's cross from the right found the midfielder ghosting into the six-yard box, and his header — placed rather than powered — left Diogo Costa rooted. It was Merino's first World Cup goal, scored in the manner of a man who had been waiting his entire career for precisely this ball.

The possession paradox

Spain finished with 68% possession and 847 completed passes. Portugal managed 287. These are numbers that should produce a comfortable victory, yet for most of the match they produced only frustration. Luis de la Fuente's side probed and circulated, finding pockets of space that led to other pockets of space that led, ultimately, to Diogo Costa's gloves or a Portuguese shin.

The problem was not creation — Spain generated 2.3 expected goals to Portugal's 0.4 — but conversion. Nico Williams struck the post. Lamine Yamal, still only 18 and playing like he has done this for a decade, saw two efforts saved. The finishing was profligate, the approach play immaculate.

Ronaldo's quiet exit

Cristiano Ronaldo, 41 years old and appearing in what was almost certainly his final World Cup knockout match, touched the ball 34 times and had one shot. He was not poor so much as peripheral, a monument to past glories stationed in an attack that could not supply him. When he was substituted in the 81st minute, he walked off without protest, the crowd's applause more valedictory than hopeful.

Portugal's strategy — defend deep, counter when possible, hope for penalties — was coherent but ultimately passive. Roberto Martínez set up to survive rather than compete, and survival has a way of running out when the opponent keeps knocking.

Our take

Spain are now the clear favorites. Not because they beat Portugal, but because they beat Portugal while playing at 70% intensity and still looked two classes above. Germany or Croatia await in the quarterfinals, and neither will fancy their chances against a side this technically fluent and tactically mature. Merino's header was beautiful, but the real story is that Spain have figured out how to win when beauty alone is not enough. That is what separates contenders from champions.