The Portuguese won the 2025 title in a penalty shootout after a 2-2 draw in Munich and the teams face off again in the World Cup knockout rounds with Spain looking to avenge that loss.
"I've seen that match, but in the last week again I reviewed it just because we're seeking to remind ourselves of the features our opponent has," he told reporters on Sunday.
"The details will make a huge difference tomorrow, so the more we know the opponent the better off we will be. We want to know them very well and be very aware of their strengths, of which they have many and their weaknesses, which every team has.
"I think the game will be very different, not only in a football sense. Our football idea is similar, we like to have the ball but it's the World Cup and a World Cup is a unique opportunity.
"It's a knockout game and we have to play in the best way to get victory and that's what we're going to do and not let the opponent control the game."
Cristiano Ronaldo, who the Spain coach called "a genius", was one of Portugal's scorers in the most recent meeting between the teams and De la Fuente conceded the 41-year-old remained a threat to his side's hopes of progressing to the quarter-finals.
"As a footballer he is someone you have to take care of, he can change a game in the moment," said De la Fuente.
"It's not that we have to do man-to-man marking, but in certain areas we have to be aware he's there.
"Cristiano has quality and class and in any moment he can be decisive. I would prefer if he didn't play, of course, but I think he will."
Spain's progress through the tournament so far, which saw them top their group before defeating Austria in the last 32, has prompted De la Fuente's side to be likened to the team that won the title in South Africa in 2010.
"To think that we might be compared to a squad from the past really makes me proud," he said.
"That was a spectacular team, a brilliant team. My players, no one is giving them anything for free.
"We are on our way and, whether we win the title or not, it's a very challenging thing to do.
"We have footballers who have a whole career ahead of them, they're just at the start of this. Recognition is given for titles, for championships and these players are always going to be in the fight for those.
"Whether they win this, that's challenging to predict."