When Cristiano Ronaldo whipped that vicious, nigh-on unstoppable free kick beyond David De Gea on Friday night, Spain howled and neutrals around the world rejoiced.
The game had finished in a draw but football had been the winner: Spain, for their part, had shown glimpses of their fluent, high-octane best and if that was an appetiser for match-ups between this World Cup's big guns then the knockout stages, when they begin in a week and a half, will be something to behold.
Yet it is not that simple and, for Spain, the pivotal second matchday in Group B brings with it an element of doubt. You can be as slick as you want, have all the stars you like, and can have shown immense character in shrugging off the last-minute removal of your manager -- but one slip now has the potential to render those advantages ancient history.
That is the danger facing Fernando Hierro's team against Iran. On paper this was, at the outset, probably the safest-looking bet of their fixtures in a relatively innocuous group. But Ronaldo's equaliser was not the only last-minute gamechanger to alter the odds four days ago. Aziz Bouhaddouz's stoppage-time own goal turned one point into an unexpected three for Iran against Morocco and means that, sitting top of the pile, the Asian side can suddenly smell blood.
"This team is very proud and [full of] heart," Isco told media at Spain's Krasnodar training base on Monday. We are really looking forward to doing things right. We will grow up against adversaries and we will not crumble at any time."
There is certainly the school of thought that champions tend to grow into a tournament. It was something Spain failed to do during their disastrous 2014 campaign in Brazil, when they certainly did crumble, Netherlands and Chile sending them home in resounding fashion. So it will augur well if they can see off Iran, dogged and supremely drilled by Carlos Queiroz, convincingly.
A mini-trend has emerged in the early stages of this World Cup whereby teams with long-serving coaches have tended to perform above expectation: look at Iceland under Heimir Hallgrimsson and Switzerland under Vladimir Petkovic. Queiroz, in charge of Iran for the last seven years, is the stand-out name on that list. His players know their roles and have experienced minimal upheaval. If Spain, whose preparation has been the polar opposite, overcome Iran's organisation and show cohesion of their own their momentum could pick up tantalisingly.
The danger exists, too, that this is effectively a free hit for an Iran side that can now afford to lose a game. Their mini-cup final always looked likely to be against Portugal, Queiroz's homeland and the country once managed by him. He will fancy his chances of masterminding a result against them; in the meantime perhaps Serdar Azmoun, the Rubin Kazan forward and "Iranian Messi" who will be lining up in the stadium where he plays his club football, and free-scoring AZ winger Alireza Jahanbakhsh can cut loose and express themselves with the pressure slightly relieved.
Spain will want to avoid their final group match with Morocco being dogged by too many variables and they are far from being the only big name in this position. Argentina, Brazil and Germany managed only two draws between them on the first matchday and all now find themselves skating on thin ice.
The Germans would probably prefer a softer opponent than Sweden when bidding to reignite their campaign; for Argentina, Croatia will pose a banana skin that could yet make for a decisive tie against Nigeria in a week's time. None of the favourites has demonstrated that they have an automatic right to a place in the round of 16. These are ifs and buts; that, though, is the very fascination in this second round of games. Everything can go up in smoke -- or it can become turbo-charged.
"Everyone is very motivated," Isco continued. "You have to be thorough and prepare very well when you face these teams."
That is the crux of it. The challenge now is as much won with sharp minds as with sparkling feet. Any drop-off from Spain at this stage, and the World Cup may have to look elsewhere for more of the instant-classic fare to which they contributed in Sochi.