The Villarreal manager is preparing for an emotionally charged reunion with the Liverpool boss, but insists their friendship will be put aside once the teams take to the pitch.
“Beyond the personal emotion of meeting Andoni, it is a source of pride for the club to play against this team, in this stadium and in the Champions League. We must approach it without fear, with courage and enjoying the occasion,” Pérez said.
The pair have a long-standing relationship and know each other well, having worked together previously with Rayo Vallecano. However, Pérez revealed that they had not spoken since the Champions League draw brought their teams together.
“We are quite similar and we grew up in a part of the country characterised by introversion. Since the draw came out, I haven't spoken to him. We will greet each other timidly before the match and afterwards, probably whoever isn't happy with the result will run away,” he joked.
Their familiarity could make tactical surprises difficult, although Pérez believes both sides will largely remain faithful to their established identities.
“Andoni knows me very well and I know him too. These days, coaches have all the information and data they need to understand their opponents. I don't think there will be many surprises, but we will try to make that mirror between the two teams work in our favour,” he said.
Villarreal know they face a demanding evening against a Liverpool side expected to press aggressively and maintain its intensity throughout the match. Pérez believes his players must accept that challenge rather than allow the atmosphere at Anfield to unsettle them.
“In a stadium like Anfield, similar in some ways to Dortmund, we must accept that the opposition will press us and may maintain that intensity from the first minute until the end. We have to recognise their strengths, find our own and try to impose ourselves.
“Accepting that there will be pressure, that they will run and create chances, will help us remain calm within that chaos.”
Pérez also stressed that Liverpool's set-piece threat would require particular attention, describing the importance attached to dead-ball situations in English football as almost cultural.
“In England, set-pieces go beyond tactics: they are almost a cultural issue. When there is a throw-in or a corner, it is celebrated. We know how important they are and must avoid conceding those situations.
“We analyse the routines and give the players all the information they need to defend them. Tomorrow we will have to be especially prepared.”
The Villarreal coach is reluctant to abandon his team's usual approach simply because Iraola knows him so well.
“If you change the way you play to surprise someone who knows you well, you risk tripping yourself up. The key is to find a balance. I think there will be few surprises, although we will try to adapt if something new appears. The identities of both teams are clear and neither coach will try to hide them.”
Villarreal have created plenty of chances in the early part of the season but have not always converted them. Pérez acknowledged that the gap between their expected goals and actual scoring output had affected confidence.
“When expectations are not met, they can become pressure that is difficult to manage, and that is affecting us, at least morally. We will try to recover our enthusiasm, keep creating chances and be more clinical.
“I am convinced that, with the forwards we have, we will improve our efficiency.”
For Pérez, the challenge is to turn that conviction into a performance against one of Europe's most demanding opponents, while setting aside a friendship that will resume after the final whistle.