When extra-time got going so did Spain. Suddenly they started making the chances that had evaded them for 90 minutes. Cesc Fábregas, Pedro Rodriguez and Jesús Navas, the three substitutes, dragged them towards Rui Patricio's goal; Andrés Iniesta started to take control. His shot was saved, Navas's shot too, but they were creating clear chances for the first time in the semi-final against Portugal. It was as if they felt time was running out. The conclusion seemed clear: Spain did not want a penalty shootout.

At the final whistle, the psychological advantage appeared to be Portugal's; all the more so when Xabi Alonso's opening penalty was saved. But then as one Spanish player put it: "We had an advantage ... we had Iker Casillas." Easy to say with hindsight and, a place in the final assured, the goalkeeper made a gesture as if his stomach was churning and pulled a face, insisting: "Mentally, I suffered." And yet it was true. There is comfort in Casillas.

Spain were trailing. João Moutinho stepped up next. Casillas flew to his right to save, the slate wiped clean, the chance to start again. To live again. The feeling was familiar. "Iker has that ability to appear in decisive moments, that magic to make incredible saves in the biggest games, when you're teetering on the edge," says Alvaro Arbeloa.

Already a European champion with Real Madrid in 2000, Casillas really announced his arrival in 2002 when he became an accidental hero. A decade later, everything has changed, except the fact that he is still appearing when most needed.

That year, he came on as a substitute with 23 minutes remaining in the Champions League final after César Sánchez picked up an injury, and rescued Madrid. Little over a month later, he became Spain's first-choice goalkeeper at the World Cup – after Santiago Canizares dropped an aftershave bottle on his foot, severing tendons – and rescued Spain. The selección beat the Republic of Ireland on penalties and Casillas was beatified. Again, he had appeared just when needed: Juanfran had missed, Casillas made good the mistake, saving from Kevin Kilbane. His new nickname, and it has stuck, was Saint Iker.

He never left the Spain team again – he has more caps than anyone and a victory on Sunday would be his 100th – and after the 2006 World Cup he became captain. On the night that Spain's historic cycle began in a penalty shootout with Italy in the Euro 2008 quarter-final, Dani Güiza had missed his; Casillas saved the next one, this time from Antonio Di Natale. He had already saved from Daniele De Rossi.

Casillas has become Spain's safety net. Before Casillas, Spain had been involved in three penalty shootouts, winning one. They even lost to England. With Casillas, they have been involved in four penalty shootouts, losing just one of them. He has saved five penalties. The total saved by other Spaniards in shootouts? None. Spain had faced 14 penalties; 13 went in, one over. And at the last World Cup, Casillas saved another penalty, against Paraguay in normal time.

"He is instinctive and has great reflexes, speed and power in his legs," says the goalkeeping coach Paco Ochotorena. "He has two qualities that most stand out: reflexes and one-on-one," Arbeloa said. "He can stop anything. He's quick, agile, intuitive and well-positioned. One-on-one he is spectacular: he stays up and reads the striker's intentions very well."

Ask Arjen Robben. Twice he got through in the World Cup final; twice Casillas stopped him. Afterwards, there were calls to name a street in Madrid: The Mother That Gave Birth to Casillas Street. In his town of Móstoles, south of the capital, there's already a Casillas Avenue.

Against Croatia in the final group game here, Ivan Rakitic's header could have put Spain out. Casillas saved it. He has played his part in Spain's run of eight consecutive clean sheets in knockout matches; he is just 74 minutes off Dino Zoff's record for not conceding a goal at the Euros, set between 1968 and 1980.

The Rakitic save was shown over and over but TV replays are worthless in appreciating Casillas because they remove the quality that makes him extraordinary – the sheer speed.

Afterwards, Vicente del Bosque said: "We knew they would get a chance, but Iker was there as always." "He is not a goalkeeper," Slaven Bilic said, "he is a hero, a leader."

Bilic was right but it is a leadership worn lightly. Much like the way he handles the pressure of penalties. At key moments, though, he has reacted. Casillas admitted that had the Euros been in 2011 the tension between Madrid and Barcelona players might have proven problematic. One of the reasons those tensions are less incendiary now is that Casillas contacted Xavi Hernández and Carles Puyol seeking a solution. José Mourinho was not happy; Del Bosque was grateful.

"Iker's not your typical goalkeeper who keeps shouting even under water. He'll correct your position and alert you but he's not one of those who is constantly talking," Arbeloa said. "He has always been a captain who shares responsibility and authority.

"With time he's learned what team- mates expect from him as captain. He's relaxed, calm. I'm not sure if he's the kind of guy who has the classic leader's character, probably not, but he's a very good captain."

Results suggest so. Since Casillas took the armband, Spain have won everything. No one has captained as many European Championship games. Only three goalkeepers have captained World Cup winning teams: Zoff in 1982, Gianpiero Combi in 1934 and Casillas in 2010. No goalkeeper has ever won the three major tournaments in a row. No captain ever has. On Sunday night, Iker Casillas will seek to become the first.