In the final moments of the game, Spain used a brilliant tactic to break the hearts of the Portuguese and advance to the World Cup quarter-finals. Substitute Mikel Merino’s stoppage-time goal sealed a hard-fought 1-0 victory over Iberian rivals Portugal at AT&T Stadium on Monday, kicking off Cristiano Ronaldo’s storied World Cup career.In a cautious duel that seemed destined to go into overtime, the decisive moment came in the 91st minute. Freshly tied up Arsenal midfielder Merino showed elite composure. Merino quickly restarted play as the Portuguese defense lay motionless, arguing over the referee’s whistle. He took the ball away, sprinted into the penalty area and coolly passed Ferran Torres’ cool pass back to the helpless Diogo Costa.It was a stroke of genius from Luis de la Fuente, who introduced Merino in the 85th minute. The midfielder endured an injury-plagued season but still helped Arsenal win a first Premier League title in more than two decades, proving to be Spain’s ultimate wild card.The victory was a historic milestone for La Roja, who reached the quarter-finals for the first time since their triumph in South Africa in 2010. An impenetrable defense was the basis of this victory. Goalkeeper Unai Simon extended his all-time World Cup record to 609 minutes without conceding, making Spain the first team in World Cup history to keep clean sheets in six consecutive matches.It was a painful, tearful farewell for Portugal and the 41-year-old Ronaldo. The international icon, who has scored 146 goals in 233 games, was stymied by a disciplined Spanish defense throughout the night.Ronaldo’s iconic hat-trick earned the two teams a 3-3 draw in Russia, eight years after a 105-year-old rivalry ended with defensive courage and quick thinking. Spain will now travel to Inglewood, Calif., to face either the United States or Belgium on Saturday.