New Delhi, July 8 -- As Spain continued to probe, to find a way through the gritty Portugal defence, late in their World Cup Round of 16 game at Dallas on Monday, there seemed a certain amount of caution. Favourites going into the trans-Iberian clash, Spain didn't want to be surprised by Portugal at the other end. Those interested in past events influencing the present would have cast their minds back to 2018 when the last time the two sides met in the World Cup in the group stage. Then, Cristiano Ronaldo was a one-man army, giving Portugal the lead and then unleashing a stunning 88th minute free-kick to complete his hat-trick and force a 3-3 draw. This time there was no real concern. Ronaldo, 41, had looked a shadow of his menacing self for some time and shorn of confidence to make life difficult for the Spanish defence, he cut a forlon figure. Lamine Yamal though had sprung to life since Nuno Mendes was forced off due to injury in the 55th minute. Nelson Semedo, his replacement, was struggling to deal with the movement of the Spanish teenager on the right, even with support from Joao Felix. It appeared Portugual will drag the tie into extra-time. Spain coach's last gasp move was his last two substitutes, Mikel Merino and Fabian Ruiz coming on. Midfielder Merino would have been expected to start, but his Arsenal season had been blighted with injury and he was struggling to make it to the starting line-up. But Merino's temperament and skill in the rival penalty box had helped Arsenal build up towards their first league title for 22 years. Merino had hardly come on when Bernardo Silva, also a substitute, made a lunging challenge to take a yellow card. That was in Spain's half. Silva's second foul on Merino was advanced, into the Portugal half. The tall midfielder quickly took the kick, and as Spain passed down the middle, slipped between two defenders to be perfectly placed to receive the pass from fellow sub Ferran Torres and whip it to the right of a diving Diogo Jota. Portugal had raised hopes with a few efforts, but none that could trouble goalkeeper Unai Simon, who has now gone a record 609 minutes without conceding a goal in World Cups. That includes six matches in this edition - 511 minutes. It was an irony that Portugal's best chance deep into stoppage time desperately chasing an equaliser came from one of the shortest men on the pitch. Silva's header skimmed over the bar. It was telling that their tallest player had had few touches in the attacking third. Ronaldo, 41, signed off with 233 caps and a world record 146 goals for the country. While his teammates were tireless in their mostly defensive duties, Ronaldo struggled, his best effort having been a feeble flick that Simon collected with a flourish. He had earlier not taken a shot from inside the box. Ronaldo had announced this would be his last World Cup. Still, Portugal manager Roberto Martinez inexplicably left him on the field for the entire game. A younger and faster substitute - Goncalo Ramos was an unused sub having scored in the last 32 win over Croatia - would have put more pressure on the Spanish defence. Spain would have controlled the game far better if only Mikel Oyarzabal had not steered an easy chance across Costa's goal in the eighth minute. In the end, they were left to wonder what would have been if they had rotated Ronaldo....