This video can not be played Spain into quarter-finals after Merino's late winner against Portugal. In 2010, Spain dazzled the football world with their tiki-taka on their way to World Cup glory in South Africa.

Powered by the midfield brilliance of Xavi Hernandez and Andres Iniesta, and the goals of David Villa, they became one of the most iconic sides to have played in the tournament's storied history. With their strong Barcelona core and the tactical acumen of Vicente del Bosque, they secured their first-ever title with short, intricate passes and relentless movement, defeating the Netherlands 1-0 in the final.

Spain now stand three wins from a second triumph after defeating Portugal 1-0 in the last 16 on Monday - just like they did in Cape Town 16 years ago. But if Spain are to get their hands on the trophy again in New Jersey on 19 July, they may have their defence, rather than their attack, to thank.

"This team knows how to compete," Spanish football expert Guillem Balague told BBC Sport. "It is a group that is committed, they all think the same way." Luis de la Fuente became Spain head coach in 2022.

Spain possess an array of attacking talent and midfield riches that would be the envy of most nations. Mikel Oyarzabal has scored 17 goals in his past 17 starts for La Roja and 18-year-old wonderkid Lamine Yamal is back to full fitness, while Pedri continues to pull the strings in midfield with support from 2024 Ballon d'Or winner Rodri.

Yet it is at the other end of the pitch where the Spaniards have built the foundations of their latest World Cup challenge. Luis de la Fuente's side have reached the quarter-finals without conceding a goal and are the only team yet to be breached at the tournament after co-hosts Mexico shipped three against England in the last 16.

They are the first team in World Cup history to keep a clean sheet in six consecutive matches, breaking clear of the previous mark set by Italy (1990) and Switzerland (2006-10). They have now gone 10 hours and nine minutes without conceding in the competition - stretching back to a goalless draw in the last 16 in 2022, when Morocco advanced through penalties.

"This is the result and fruits of collective work - great defensive solidity of course," said De La Fuente after their win against Portugal. "There is solidarity, effort, sacrifice and everybody runs for one another. Every football idea is present very clearly, but what is beautiful is the attitude these footballers show, they are committed to the cause."

The one club man who is Spain's under-the-radar hero. That defensive solidity begins with Unai Simon. The Spain goalkeeper continues to rewrite history as he extended his remarkable run without letting in a goal at the World Cup to a record 609 minutes, keeping Cristiano Ronaldo and company at bay in Dallas.

"Portugal dictated most of the game, but Rafael Leao did not offer that extra spark, neither did the other substitutes," said Balague. "Spain defended in numbers and collectively, they tracked back a lot. They individually sorted out problems. So we haven't needed a miracle save from Simon."

During this tournament, Simon has surpassed Walter Zenga's mark of 517 consecutive minutes without conceding for Italy, as well as his compatriot Iker Casillas' benchmark of 476. Ahead of Simon, Aymeric Laporte and Pau Cubarsi are at the heart of their defence, while Pedro Porro and Marc Cucurella provide the width from full-back.

That back-four has started three of Spain's five matches at this World Cup so far, with Marcos Llorente deputising for Porro at right-back in the other two. Balague added: "It also helps that Rodri is reaching his best version and he has had two extraordinary games - he is the lighthouse of the team.

"The partnership between Laporte and Cubarsi is perfect for the way Spain plays - moving the ball around, driving with it, and defending with a lot of space in behind." Spain are yet to concede a goal at this World Cup.

Spain's journey since their 2010 World Cup triumph has not exactly been smooth sailing. Although they retained the European Championship in 2012, their subsequent World Cup campaigns have brought little joy as they suffered back-to-back group-stage exits before being eliminated in the first knockout round four years ago.

But now, returning to the tournament as reigning European champions, Spain have a squad that looks capable of returning them to the pinnacle of world football. "It wasn't a great display but you feel there is so much more to come from Spain," said former England striker Chris Sutton on BBC Radio 5 Live. "The fact that they are not conceding as well is ominous for other teams. Their toughest test will come against France if they both win their games.

"I think Spain are capable of beating France but they'll have to be near perfect on the day." But before that, De La Fuente's side will look to keep their good run going when they meet either co-hosts United States or Belgium in the quarter-finals on Friday.