Former Republic of Ireland international Niall Quinn believes Giovanni Trapattoni's side can pull one of the biggest shocks of Euro 2012 and beat Spain in Gdansk on Thursday evening.
The Euro 2008 and World Cup 2010 champions will look to book their place in the last eight and end Ireland's hopes of joining them but Quinn cautioned the result was not as clear cut as many are predicting.
"[Ireland are] going into the game on a downer after a bad result against Croatia and another defeat will mean the end of their tournament," Quinn told the Telegraph.
"There was a real sense of deflation after the opening game and understandably so because it was a poor team performance.
"But we shouldn't start thinking it is impossible to beat Spain. It can be done. If Ireland are going to pull off the biggest shock of the tournament they need to improve from one to 11.
"The full-backs have to get involved more going forward, the centre-backs have to dominate, they cannot let any of the Spanish players have an easy ride as they did against Croatia.
"The midfield are going to have to work harder than ever before to shut them down, the wide players are going to have to add some creativity and drive down the flanks and the strikers are going to have to have far more cohesion than they did against Croatia.
"To be blunt, it's not an easy task, but if I look at previous tournaments I was involved in, sometimes a player can come in and be the spark everything needs to ignite - like Holland in 1988 when they brought in Marco van Basten after a poor first game and Italy in 1990 when they brought in Salvatore Schillaci."
Spain coach Vicente del Bosque surprised many with his line-up for the opening game against Italy when he named a team without a single specialist striker in it.
But Ireland striker Robbie Keane is confident he and his team-mates will be prepared for all possibilities.
"We will prepare for if there are six midfielders and if there are strikers also," Keane told a press conference on the eve of Thursday's game.
"The manager will have videos on both situations and I am sure we will be well aware of how to play against them.
"We know no matter who they play, it will be a tough ask because the players they have are world-class players, and they have probably six of the best midfielders in the world.
"Listen, it's going to be tough, but we have to believe we can go into the game and get three points, and in the worst case scenario, we get a point."