ARLINGTON, Texas - Mikel Merino scored a dramatic 91st-minute winner as Spain beat Cristiano Ronaldo's Portugal 1-0 in the FIFA World Cup round of 16 on Monday afternoon.

A tight, nervous match looked to be heading for extra time until two Spain substitutes combined for the game's only goal. Ferran Torres played in Merino, who finished low past Portugal goalkeeper Diogo Costa.

Earlier, Mikel Oyarzabal had missed a glorious opportunity to put Spain ahead, before Ronaldo - who said before the match that this would be his last World Cup - saw an effort palmed away by Unai Simon, and Costa denied Alex Baena with a fingertip stop.

Simon denied Ronaldo again before halftime, and Nuno Mendes' deflected effort hit the crossbar, before a cagey second half with few clear chances was decided by Merino's cool finish.

Spain will now play either the United States or Belgium in the quarterfinals in Los Angeles on Friday.

Ronaldo fumbles final chance on World Cup stage

Four years ago, it appeared Ronaldo's World Cup journey was over when the Portuguese legend, then 37, left the field in tears after Portugal's upset loss to Morocco in the quarterfinals. Given another opportunity and nearly unlimited playing time by head coach Roberto Martinez, Ronaldo had a chance to change the ending. It did not happen.

In what he revealed was his final World Cup match, Ronaldo managed only 19 total touches: 12 in the first half - the fewest he has ever had in the first half of a World Cup match - and only seven in the second, none after the 80th minute.

He attempted three shots in 90 minutes and nearly scored in the 37th minute after Simon blocked a Joao Felix shot in his direction. But he could not get much on a quick rebound, and Simon was able to make a diving save. Portugal ultimately generated just 0.58 expected goals from 10 shot attempts, and Martinez elected to keep Ronaldo's backup, Goncalo Ramos, on the bench despite Ramos' late heroics against Croatia.

It felt as if the Ronaldo era had ended in 2022 in Qatar. In five matches and 291 minutes in the 2022 World Cup, Ronaldo scored only once, via a penalty. Ramos, his presumed replacement, also recorded a hat trick in his brief absence; it felt like a passing of the torch of sorts. Instead, the 41-year-old was back captaining the lineup for much of the Martinez era.

Martinez was complimentary of his leadership all the way to the end, and Ronaldo also scored a pair of goals in a blowout of Uzbekistan. But in four matches against teams that actually reached the knockout rounds, he scored only a penalty against Croatia. More importantly, Portugal scored only two goals in his 351 minutes. And despite a brilliant defensive performance against Spain, they were still eliminated.

Few legends have nailed their final act, and Ronaldo does not lack for other honors. The five-time Ballon d'Or winner has been part of eight league title-winning teams and, more notably, five Champions League winners. But his World Cup tally was light compared with some of the game's other stars, including longtime rival Lionel Messi. He was a solid role player for the Portugal team that finished fourth in 2006, but Portugal have won only one knockout round match since.

Though Martinez's three-and-a-half-year tenure did feature a Nations League title, it will be mostly defined by the World Cup risk he took on Ronaldo and the fact that it did not pay off.

Subs make the difference for Spain

Spain coach Luis de la Fuente was right. Again.

Nobody has doubted the quality of Spain's starting XI, or even the presence of good, solid alternatives among the substitutes. But a legitimate question has been: Do Spain really have top-level game-changers who can win games off the bench? With fitness issues at different times for all of Spain's four wingers, backup forward Torres misfiring, and third-choice Borja Iglesias not yet given a single minute to show what he can do, it felt like a fair point to raise.

In the 91st minute Monday, Torres and Merino dispelled those doubts. Another substitute, Fabian Ruiz, gave the ball to the outstanding Rodri, who found Torres. His two touches were sublime: one to control the ball, and another to thread a pass through to Merino, who had expertly timed his run to stay on side. Merino finished, first time, into the bottom corner, before running off to the corner flag to celebrate.

"Mikel Merino never lets you down," De la Fuente said after the match. "He won us the Euros. He's a huge player; he's one of the best in the world in his position. We're lucky to have players on the bench who would be starters in any other national team."

The timing of the goal meant Spain knew they were headed for the quarterfinals. And De la Fuente, once more, was vindicated. He has said, more than once, to the media at this tournament: Spain's squad, not the starting XI, would see them go far. "We talk about it a lot on the inside," he said last week. "At the Euros, the most important games were decided by the players who came off the bench."

And now they have done it again.

Martinez lacked new ideas, and Portugal paid the price

One of the most interesting parts of a World Cup is seeing so many matchups you do not normally see. Spain-Portugal was the opposite - they share a border, club teammates and similar continental styles, after all, and it showed.

For most of 90 minutes, neither could surprise the other. Spain could not filter the ball easily to star Lamine Yamal, even after Portugal's star left back, Mendes, left the game because of injury. Portugal, meanwhile, was allowed to move the ball on the wings, but nothing came of anything in the middle. The teams combined to block five shots and 14 passes; from Oyarzabal's miss in the eighth minute until Merino's goal in the 91st, neither team attempted a single shot worth more than 0.2 expected goals.

It felt as if both teams assumed the match was going 120 minutes until it did not. Spain initiated a quick restart after a foul, and two substitutes caught Portugal's defense flat-footed for probably the first time in the match. A new idea paid off. Six minutes of defense later, Spain had advanced.

Against any opponent better than Uzbekistan, Portugal struggled to create consistent opportunities in the World Cup. Despite the fact that Ronaldo produced no aerial presence in the World Cup - he attempted only four aerial duels in the first two matches and none in the final three - Martinez never looked to Ramos.

"When you're a team and you need a goal, you can't take Cristiano Ronaldo off," Martinez said, echoing comments he made after Portugal's draw with Congo DR, a costly result that meant they had to play Spain in the round of 16. "He's a presence, he opens space, a dead-ball situation, anything in the box, it would make no sense."

Ronaldo once did all of those things, but it has been a while. He averaged just 3.7 shots and 3.3 duel attempts per 90 minutes in this World Cup. In the 2010, 2014 and 2018 World Cups - when he was indeed still one of the best forwards in the world - Ronaldo averaged 5.9 shots and 11.5 duel attempts, respectively.

That he was not at his best at age 41 should not be a surprise, but Martinez's refusal to acknowledge it both forced Portugal to play a tougher round-of-16 match and got them eliminated from it. Their opponents found the ideas, and the goals, that they lacked.

Yamal underwhelms against strong opposition

Yamal said it himself, just the other day: Portugal's Mendes is the toughest opponent he has faced. "He's very good," the Spain winger said, when asked to name a left back. "I like playing against him."

For 56 minutes here, it did not look as if Yamal was having much fun. Mendes did a good job of keeping Yamal quiet. There was only one first-half shot, saved easily by Costa. Yamal did not once manage to beat Mendes one-on-one until the second half, on 52 minutes. Even then, his ball into the box failed to find a teammate. "For sure, Nuno Mendes is the best left back in the world at this moment," Portugal coach Roberto Martinez said postmatch.

Yamal's World Cup is still waiting to catch fire. As other stars - Messi, Kylian Mbappe, Erling Haaland, Harry Kane - have delivered, Yamal has been playing catch-up, first with his fitness, and then with his form. His early goal against Saudi Arabia was a great moment, but one decisive group stage contribution is not nearly enough for a player this talented.

When Mendes went off injured after 56 minutes, there was hope for Yamal. Perhaps his replacement, Nelson Semedo, would be a less demanding opponent. But even then, Yamal kept probing without much success.

"Lamine loves these games," coach Luis de la Fuente said Sunday. "He loves the responsibility, being in the spotlight, taking the initiative."

Yamal could not do that against Portugal. Instead, he looked more like what Ronaldo called him before the match, with what sounded like intentionally faint praise: "A player with a big future."

Spain's remarkable defensive record continues

Spain's attack has sputtered a bit in the World Cup: Of the 10 teams that have played five matches to date, their nine goals are ahead of only Portugal and Paraguay. Their goal differential, however, trails only France. That is what happens when you never give up a goal.

With defensive midfielder Rodri playing his way back into dominant form, with Simon making the occasional excellent save, and with the back line of center backs Pau Cubarsi and Aymeric Laporte, left back Marc Cucurella and either of two right backs (Pedro Porro and Marcos Llorente) combining to win 57% of their duels, Spain have been untouchable in the back thus far. They already put pressure on their opponents by controlling the ball for a majority of every match, but when called upon, their defense continues to respond.

Against Portugal on Monday, Spain briefly played with fire late in the first half. Simon misread a cross and was forced to block a Joao Felix shot and save a rebound from Ronaldo in the 37th minute, then Mendes fired a deflected shot off the bar in the 41st. But Portugal generated very little from there, and Spain recorded its fifth clean sheet in five tries.