Giovanni Trapattoni has warned his Republic of Ireland side that they must avoid mistakes against Croatia on Sunday.
The 73-year-old will have his squad well-prepared but has told them that they must be ready for anything if they hope to succeed.
"You can prepare for a match in the best way you can, but I always watch matches and I prepare very well, and then there are unpredictable situations," he told reporters.
"This is something unpredictable and something unpredictable can happen in each match. We are really confident, but we have to be aware of that unpredictability.
"The most important thing is what you feel. We all expect victory, of course, but the question is whether you can avoid mistakes. That is a huge concern because in each match, you want to avoid mistakes.
"In each circumstance, the Irish nation is confident about this team. They fully believe in us."
Despite their role as underdogs, Trapattoni feels that a win for Ireland in their opening game could set up a memorable run in the tournament in Poland and Ukraine.
"Of course, the first match is critical," Trappatoni said.
"If you win the first match, you get momentum and enthusiasm and in this way you can avoid criticism and you are still confident and maybe you can reach your goal.
"I have said already last week, 'never say never'. Of course, the final result depends on the players, their creativity and their talent. That's why you have to believe in it.
"For me and for (assistant manager) Marco Tardelli, we have given Irish people what Ireland has asked for. We got here because we were fully determined to get through qualification."
Related Articles

Matildas ‘can’t wait’ to return against Ireland

Irish eyes not smiling on O’Neill, yet
