The Italian veteran refused to name his starting XI but insisted that his squad will take the game to La Roja and will need some luck to get something from the match
The Boys in Green are massive underdogs to get anything against the world champions and the Italian tactician is set to leave naming his team until the last minute.
"We will play to win," Trapattoni said at the pre-match press conference in Gdansk.
He added: "But we know also it is difficult because we know Spain are the world champions and they have very important players.
"In football, over 10 months it's possible for a strong team to win, but in 90 minutes, anything is possible."
Ireland are currently bottom of Group C after losing their opening game to Croatia 3-1. Holders Spain began with a 1-1 draw against Italy and are hot favourites to seal all three points this evening.
Trapattoni avoided giving any hints as to what his line up would be amid suggestions that Robbie Keane will start as a lone striker in front of a five-man midfield.
"Our objective is to be offensive and try to win the game, but at the same time, we need also to find a way to help the midfield because sometimes we have suffered in this situation," said the 73-year old.
The Italian, who has been in charge of Ireland sine 2008, said he is 'proud' to be the Ireland coach and said his team can spring a surprise against the holders.
"We have achieved results not only with heart because we have met France, Bulgaria, Italy, many other teams and we played the same. We play our football.
"It's creative enough and it's technical enough. Maybe Spain have one or two more creative players, but football is not only about creative players.
"I have already said we have to believe in our quality, our attitude, our performance," he said.
Whilst he refused to name his own team the former Juventus manager said he expected his Spanish counterpart Vicente del Bosque to play with a striker after the 'false nine' tactics employed against Italy.
He concluded that Ireland will need some fortune to reach the knock out phase but reiterated his belief in the players.
"Today, football is about balance on the pitch and strength with attitude and also luck," he said before concluding "We have attitude, mentality, commitment, technical ability. We don't make bets, but I think we can win. Why not?"
Ireland take on Spain tonight in Gdansk with the match kicking off at 19.45 BST.