Sean St Ledger believes Republic of Ireland need to take Croatia just as seriously as Spain and Italy, and has warned against seeing it as their easiest group game.
Giovanni Trapattoni's men face a tough test to emerge from Group C and will need to secure at least one famous win to make the last eight.
But the defender does not think that Sunday's clash with Croatia is necessarily their best chance of achieving three points.
He said: "We played Croatia last year and they are a very good team.
"They have a lot of talent in their squad and that game is going to be the same as the Spain and Italy games. It is going to be a very tough game for us.
"Everyone is really excited for this game against Croatia. It has been 24 years since we have been in this tournament and we have got a very tough group."
But despite being drawn against three of the top sides in Europe, St Ledger insists belief in the squad is high.
He continued: "we are unbeaten in 14 games, we have kept a lot of clean sheets and we can definitely score goals.
"Everybody is looking forward to it and hopefully we can go and get the three points on Sunday."
The Irish squad will have been together for three weeks by the time they kick off in Poznan, but the 27-year-old is enjoying the experience, having only made his debut for his country in 2009,
"It's gone really quickly, to be fair. I think it is because we have changed destinations from Portmarnock and then Italy and Hungary.
"It's been enjoyable. Obviously, these tournaments only come around once every four years, so you just have to enjoy the moment."