The Republic of Ireland were routed by Belgium in their second game of the competition at the Nouveau Stade de Bordeaux, losing 3-0 to one of the tournament favourites who rebounded in style from their own loss to the Azzuri.

All the goals were conceded after the break, with two from Romelu Lukaku sandwiching another from midfielder Axel Witsel as Ireland were utterly outclassed five days after impressing in their opener against Sweden.

The manner of the loss was crushing given it was every bit as comprehensive a defeat as those suffered by Giovanni Trapattoni's Ireland in Poland four years ago when they were no match for Croatia, Spain and Italy.

"You can start to feel very sorry for yourself and commiserate with your teammate and feel as if it is gone, or you can go and take some self-confidence from the way you played two or three days ago," said O'Neill.

"The most important thing for us is to try and put it to the side. It is never easy for a manager, never dismiss it, but most important is to reappraise and go and try and win the game. I don't think that will be as difficult as it is maybe looking from here."

Ireland will exit the tournament if they fail to to beat an Italian side that is now guaranteed top spot in the group and one which may now take the opportunity to rest some players ahead of the knockout stage.

It is a nice thought, but not one the Irish manager can entertain.

"I'm not responsible for anything that Italy might think or do. I don't know," he said. "They are going to finish top regardless now, I believe. We have to win the game. That can be our only thought.

"We must go and win it. There was talk before the tournament that if you went unbeaten and had three points then it would be enough. That is gone now. We have to win a game and we will throw absolutely everything in to it."

Ireland didn't help themselves with a timid performance, and they had little or no luck with a referee who denied Shane Long a clear penalty seconds before Belgium's opener, but this was ultimately a defeat to a much superior side.

That gulf was perfectly apparent long before kick-off with team sheets displaying Belgian players who ply their trade for the likes of Chelsea, Barcelona and Atletico Madrid and Irish counterparts who could only dream of such employment status.

"I don't think that can be my attitude going into the game and it shouldn't be the players' either," said O'Neill. "I mentioned yesterday that Belgium are as talented a team as there is in the competition. No question.

"But the goals we gave away were not great from our view. We knew that the first goal would be important. My disappointment came from the fact that against Sweden we played exceptionally well with the ball and today when we had it we looked nervous and gave it away too readily. It was coming back at us too quickly.

"We were hoping to rectify that at half-time but they broke on us from a ball bouncing around in their area from one of our free kicks. Then you start to chase the game and you get stretched. They have fine players that can punish you and that's what happened."

O'Neill did not see the incident before Lukaku's opener when two Belgian players appeared to catch Shane Long in the head with high, flying boots in their own penalty area but he revealed that his players were adamant it should have been a penalty.

"I was asked if that would have changed the game," he added. "It would have done if we scored but overall we were beaten today by a better team. We have to rectify that in few days time."