A moment of sheer tactical brilliance in the dying moments of the match saw Spain break Portuguese hearts and book their place in the World Cup quarter-finals. Substitute Mikel Merino’s strike secured a hard-fought 1-0 win over Iberian rivals Portugal at the AT&T Stadium on Monday, bringing the curtain down on Cristiano Ronaldo’s legendary World Cup career.In a cagey encounter that seemed destined for extra time, the defining moment came in the 91st minute. As soon as it arrived, Arsenal midfielder Merino showed an elite presence of mind. While the Portuguese defense remained static, debating the referee’s whistle, Merino quickly resumed play. He pulled the ball up, made a run into the box, and calmly slotted a clinical return pass from Ferran Torres past a helpless Diogo Costa.It was a masterstroke from Luis de la Fuente, who had only introduced Merino in the 85th minute. The midfielder, who has endured an injury-plagued season but still helped Arsenal win their first Premier League title in more than two decades, proved to be Spain’s latest wildcard.The victory marks a historic milestone for La Roja, who were marching into the quarter-finals for the first time since their triumphant 2010 campaign in South Africa. The victory was anchored by an impenetrable defense; Goalkeeper Unai Simón extended his historic World Cup record to 609 minutes without conceding, anchoring Spain as the first team to record six consecutive clean sheets in the tournament’s history.For Portugal and the 41-year-old Ronaldo, it was a bitter and tearful farewell. The international icon, bowing out with 146 goals and 233 appearances, was starved of service all evening from a disciplined Spanish backline.Eight years after Ronaldo’s iconic hat-trick lit up a thrilling 3-3 draw between these sides in Russia, this 105-year-old rivalry was settled by defensive grit and quick thinking. Spain now travel to Inglewood, California to face either the United States or Belgium on Saturday.