Spain midfielder Xabi Alonso is expecting a major battle as the Republic attempt to stage a Euro 2012 smash and grab raid.
The holders face Giovanni Trapattoni's men at the PGE Arena in Gdansk tonight having taken a point from their opening game against Italy, but desperate to claim a first victory to ease themselves towards the quarter-finals.
Ireland will do everything within their powers to deny the Spaniards the win they crave with their own need even more pressing, and Real Madrid star Alonso is preparing himself for a fight.
"With Irish teams, you know they are very proud. They will fight from the first minute until the last and they will play together as a team," he said.
"It's going to be a very difficult match. They know us and they know our characteristics, but we also know them because they all play in the Premier League.
"We will have to be very patient. We will have to try to score early in the game because that makes everything easier afterwards.
"It's going to be a difficult match. Anything can happen. We will have to fight from the beginning."
Trapattoni has hinted that he might tinker with his formation in an effort to stem the flow from Spain's star-studded midfield and drop one of his strikers into a deeper role.
However, Alonso revealed that manager Vicente Del Bosque is prepared for all eventualities.
He said: "In most of the games we have seen, they have played with two strikers, and if one of them drops deep, that will make it tougher and more compact in midfield.
"If Robbie Keane plays up front and Jon Walters or Kevin Doyle drops deeper, that's what we have been working on."
Del Bosque's decision to line up against Italy with six midfielders and no strikers prompted criticism despite the fact that Cesc Fabregas, the man asked to provide the goal threat, did find the back of the net.
Alonso admitted he did not know what all the fuss was about, and pointed to the result as justification.
He said: "We have used this tactic several times, it's not the first time we have used it. We know it works in a different way to when you are playing with a striker, but it can work, and we saw that in the last match when Cesc played there and scored a great goal.
"But it's not about what system you use, it's about how we play it and if the result is good, then you say the tactic was fantastic and the decision the manager took was the right one.
"We were quite pleased with how it worked."