Fernando Torres put to bed any debate about his form on Thursday as 'El Nino' scored a double to inspire defending champions Spain to a 4-0 drubbing of a gutsy but outclassed Ireland.
His double and goals by David Silva and Cesc Fabregas sent the Spanish top of Group C on goal difference from Croatia while defeat ended Irish hopes of progressing to the last eight.
Croatia - 3-1 victors over Ireland in their opening game - came from 1-0 down to draw 1-1 with Italy thanks to Mario Mandzukic's third goal of the tournament.
They will meet Spain in the last group game while Italy take on former boss Giovanni Trapattoni's Ireland - Italy could still win and not go through if all three sides end up on five points.
Ironically, Italy exited the 2004 edition at the group stage despite not losing a game - their coach then was none other than Trapattoni.
Torres, whose place in the squad had been a matter for some debate because of his woeful form with Chelsea, set the tone for their game with a superbly taken opener in the fourth minute and from then on there was only one team in it.
Torres, who came off with the game won, said that this performance showed Spain in its true light, not the one that looked rather listless in the 1-1 draw with Italy.
"We really were champing at the bit ahead of this game to shake off the draw against Italy and we saw the old Spain of 2008 (when his goal won them the title), and 2010 (the World Cup win)," said Torres.
Spain coach Vicente del Bosque, who came in for some criticism for not starting with a recognised striker in the Italy game, said that his system worked.
"Torres knows how to find the spaces, it was the perfect match, a lot of people think he could have played in the first match, but that wasn't the point," said Del Bosque.
"We have a system and we showed it works.
"People think it is important to have a striker and it is important for us as well, but it is more important to win."
Trapattoni was left bemused by the manner in which his players appeared to have frozen on the grand stage.
"The first thing that I will ask my players, is why do you crack in the Euro when you didn't do so in the heat of the battle of qualifying," said the 73-year-old coaching legend.
"I don't know, there is a difference of attitude there that I have a hard time explaining.
"Without doubt it was the pressure, the fear of a major competition. We must work on this."
Both Italian coach Cesare Prandelli and his Croat counterpart Slaven Bilic were left dissatisfied by the draw, though the latter was delighted with the point.
Prandelli was angry with his side for not making the most of their dominance of the first-half.
"I'm not angry, we're very bitter because when you play football and create chances you have to kill off the game," he said.
"But football is strange because if you give them half a chance from a cross it can change everything you've built.
"We're bitter but convinced we can go through because nothing has been mathematically decided. However, yes it's a missed chance."
Bilic, who steps down after the finals to take over Russian side Lokomotiv Moscow, was incensed by English referee and 2010 World Cup final handler Howard Webb for not awarding a penalty in the first-half for a Giorgio Chiellini challenge on Nikica Jelavic.
"I don't agree with coaches who don't comment on referees. This is very important for my job," said Bilic.
"He's so important for my job. We can talk about whether or not I'm objective or subjective and of course I'm not objective.
"But that was a clear penalty on Jelavic, I'm sure of it. The referee was not good.
"I didn't like his performance, he helped Italy. I can't say he was good, he wasn't good for us."