Spain have largely held the upper hand against their Iberian rivals, losing just nine times in 37 encounters, and they edged Portugal 1-0 in the last 16 en route to their triumph at the 2010 World Cup in South Africa.
However, Portugal claimed emphatic revenge less than five months later with a four-goal victory in Lisbon that condemned the reigning world and European champions to their heaviest defeat in 47 years.
The teams have changed little since. Nine members of Portugal's likely starting line-up at Donbass Arena in Donetsk on Wednesday featured in the game, while Spain are expected to start with eight of the same players.
Cristiano Ronaldo terrorised the Spanish back line at Estadio da Luz two years ago and would have claimed one of the finest goals of his career had Nani not headed his goal-bound shot over the line from an offside position.
The 27-year-old is not short of scores to settle against a team who can call upon five of his Real Madrid colleagues.
After match-winning performances against the Netherlands and the Czech Republic, he is finally making his mark at a major tournament and Spain's ability to keep him quiet will be pivotal.
"We will be taking special care of Cristiano Ronaldo," promised Spain coach Vicente del Bosque, whose players successfully muzzled the Portugal captain in their encounter at the last World Cup.
"It won't be an individual (marking) thing. There will be permanent support (from midfield), as there was two years ago."
The match should provide an intriguing clash of styles, with Spain likely to dominate possession while Portugal await opportunities to spring forward on the counter-attack.
Spain have lost only three times in 47 competitive matches and are closing in on an unprecedented treble of major honours, but Portugal midfielder Custodio says his side have faith in their own ability.
"We know that they are a great team, but we will look to beat them by playing to our strengths," he said.
"We'll fight to the end for a place in the final. Will this be Portugal's year? I hope so."
For the first time at the tournament, Portugal coach Paulo Bento will be obliged to change his starting line-up due to the thigh injury sustained by striker Helder Postiga in Thursday's 1-0 win over the Czech Republic.
Besiktas' Hugo Almeida is set to deputise, although 20-year-old Benfica striker Nelson Oliveira is also in contention, while defenders Pepe and Fabio Coentrao are both fit after sitting out training on Saturday to rest injuries.
Spain reported no new injuries after their victory over France, but Del Bosque must decide whether to persevere with Cesc Fabregas in the 'false nine' role or restore Fernando Torres to his starting XI.
While Spain are gunning to become the first team to win three consecutive major international tournaments, Portugal are aiming to reach a first final since their heartbreaking loss to Greece as hosts of Euro 2004.
The two sides' records in semi-finals are sharply contrasting.
Spain have never been beaten at this stage of an international competition, but Portugal have won only once in five attempts.
Even the great Eusebio succumbed to the country's semi-final jinx, with a late penalty not enough to prevent Portugal losing 2-1 to England at the 1966 World Cup.
The 70-year-old will not be present on Wednesday after being taken ill at Portugal's team hotel and going to hospital, where while being given the all-clear he will remain till Thursday.
Victory for Portugal would be the perfect get well gift.