In a dour 90 minutes, neither side managed a meaningful effort on goal, and it took over 100 before either goalkeeper was called into serious action - Portugal's Rui Patricio twice denying Spain during extra time.
But the game seemed destined for penalties and it was to be Bruno Alves who would miss the crucial spot-kick, leaving Cesc Fabregas with the chance to clinch Spain's place in the final. Despite hitting the inside of the post, the ball nestled in the back of the net to send Vicente Del Bosque's men to Kiev for a meeting with Germany or Italy on Sunday.
Cristiano Ronaldo is Portugal's captain and their most naturally gifted player. He takes responsibility for their free-kicks and had there been a penalty during normal time, surely he would have stepped up. But during the shoot-out, he was nowhere to be seen during Portugal's first four kicks. If he was being saved for the fifth, then his talents were wasted as the game was over before he had the chance to take on Casillas from 12 yards. Almost as baffling were the scenes when Bruno Alves strode forward to take the third penalty, only to be sent back by Nani as he reached the edge of the box. The Manchester United man scored. Alves, predictably, did not when he returned to take the fourth penalty.
Spain have progressed to the final of Euro 2012, arguably without hitting their best form. Winning a match without playing to your potential is often seen as a sign of greatness, but is winning a tournament without playing well more of an indictment on the opposition? Surely Vicente Del Bosque's side will have to raise their game to overcome either Germany or Italy, who remain the only team to score against them during the competititon.
Shot un-shy Ron
Cristiano Ronaldo tonight became the first player to have over 30 attempts on goal at a European Championship. The Real Madrid man took his individual tally to 35 against Spain, which means that he alone has taken more shots than four of the teams who entered the tournament. Ireland, Denmark, Greece and Croatia all had fewer shots on goal than Ronaldo, and the entire England squad could only muster 36. But the runner up for the Ballon D'or will probably live to regret not having one last effort on Iker Casillas' goal - from just 12 yards.
Portugal became the first side to shake Spain's assurance in possession. During the tournament, Spain have been allowed to dominate games, endlessly passing the ball without mounting any sort of attack. By pressing the defending champions high up the pitch, Paulo Bento's men managed to upset their neighbours' rhythm, forcing them to uncharacteristically concede possession. Tiredness prevented Portugal from continuing the tactic for 120 minutes, but it was only their decreasing fitness that allowed Spain to assert their authority.
Despite some of the best free kick specialists showcasing their skills at Euro 2012, only Andrea Pirlo has managed to find the net directly from a dead ball. Vicente Del Bosque said before this match that his side would have to avoid conceding fouls around the penalty area, with Ronaldo's renowned expertise from anywhere within range posing a serious threat. But the world's second best player has not found his range at this tournament and supporters behind the goal were more at risk than Casillas in Donetsk.
Clean sheet class
Spain have now kept a clean sheet in their last nine knock-out games at major championships, with Iker Cassillas playing over 15 hours of knock-out football without picking the ball out of his net. The record stretches back to 2006 when Zinedine Zidane netted a last-minute goal for France in the last-16 match at the World Cup in Germany.
Spain maintained their 100 per cent record in semi-finals after beating Portugal on penalties in Donetsk. The Spaniards have come out on top in each of the five times they have qualified for the last four of a major championship. The run started with a win over Hungary in the European Nations Cup in 1964 and was followed 20 years later by victory over Denmark in the same competition. Their third success came against Russia in Euro 2008, before a penalty success against Denmark at the World Cup two years ago.
Ronaldo's Spanish block
Cristiano Ronaldo's goalless record against Spain continued in Donetsk, after he failed to test Iker Casillas. The Real Madrid forward has now faced his country of residence four times but has yet to find the net. The closest he came was in November 2010 when he embarked on a mazy run and lobbed the keeper, only for Nani to head the ball in from an offside position when the ball would have nestled in the back of the net regardless. What may resonate with the precocious CR7 is the fact that adversary Lionel Messi has netted twice in three appearances against the Spanish.
Referee Cuneyt Cakir looked to have the measure of the contest before half time, but became very card happy after the interval, with no fewer than nine players ending up in his notebook by the time the final whistle was blown. Fortunately, UEFA's rules for international tournaments mean that all yellow cards from previous matches are wiped out after the quarter-finals, meaning only a red card leads to a suspension for the showpiece. It might be an idea to introduce a similar rule in the Champions League after a host of Chelsea and Bayern Munich players missed out this year due to semi-final bookings.