Mehdi Taremi will see the moment again and again in his sleep. The next time a ball is aimed perfectly at his head at the far post, with eight minutes of a critical World Cup tie to play, he will launch his 6-foot-2 frame at the ball, time his leap perfectly and send the net billowing. The next time an opportunity that glaring comes around, he will leave nothing to chance, and Spain will not be let off the hook again.
But the Iran striker got his bearings wrong, and Spain, whichever way you see their 1-0 win, got away with it. They will make the last 16 with any kind of positive result against Morocco, but they should be in the last-chance saloon, ruing the carelessness that saw them wobble after Diego Costa's fortunate goal appeared to break the most obdurate of opponents.
At this stage, a win is a win, but the alarm bells, after two Group B games, must be sounding: Spain are conceding sloppy chances and sloppy goals and struggling to sustain any consistent rhythm in attack. Can it be attributed to a familiar pattern -- the tournament favourites working their way to full pelt as the games start being ticked off -- or is there a sense that Spain's campaign is living on borrowed time?
It was certainly an eye opener to hear Fernando Hierro, who has been open and personable since succeeding Julen Lopetegui on such short notice, admit that this victory felt more troubling than one that had been taken away at the last moment.
"We were happier after the match against Portugal," he said in his postmatch news conference before straightening up and noting that Spain's position is far from unusual. "It's just a feeling. After the game, you give a flash interview and people say, 'This or that isn't working,' but we have four points. We are very demanding of ourselves, but every team will suffer."
Spain certainly are suffering -- it has been a near-constant state since those troubled days directly before the tournament -- and the question is how quickly they can be made to feel better. The threat Iran posed should not be disregarded: Carlos Queiroz's side are, as they showed when coming out of their shell, a fearsome proposition in all departments and hardly a minnow anyone should expect to brush aside. But Spain struggled when put under any serious pressure; they will still expect to face sterner, more clinical opposition as these weeks go on, and the challenge is both single and urgent. They have to improve -- and fast.
There was a delightful moment just before the half-hour mark in Kazan when Isco, with one slick swivel and gossamer touch through a gap he had no right to have seen, played Andres Iniesta through on the left of the box. The move came to nothing, but it is notable for its very memory: at the time, it seemed Spain were gaining a head of steam, starting to find their balance and play their football, beginning to work the angles and make things seem easy.
But Isco's spot of silk is notable because it turned out to be an anomaly: this Spain performance was a sluggish, unbalanced slog.
"We tried to tell them to keep calm, keep fighting," Hierro said of his speech to the players at half-time, after which Spain produced the spell that brought Costa's winner. "They had to play properly in the wide positions -- wide, wide wide."
It touched upon one of the team's biggest structural issues: the identity of the team's final attacking midfielder. This time, Lucas Vazquez was selected on the right and, indeed, told to hug the touchline and stretch the play. The problem was that Iran left no space in behind, and Vazquez, hardly a superior combination player, looked a man out of sync with his teammates when building in front of the defence.
David Silva succeeded in exerting a measure of command in a disjointed midfield, but barring a fine half-hour spell against Portugal, Spain have looked like a side that lacks spark and fluidity. "If you have a team defending very deep with 10 players, there is less space, and it is more difficult to carry out your game," Hierro said.
They need to try because Costa, who has been at his battering-ram best, might not provide a get-out-of-jail card every time Spain play. His influence has been the nearest Spain possess to a genuine focal point, genuine leadership or thrust. Those qualities have lacked in most other areas, never more so than when Taremi was left free by the defence only to fluff his lines, and if Spain are to avoid serious mishap, then the coherence of old must make a sharp reappearance.