"I was the last man on the list that day. I had no trouble taking them in training and even put a few past Niall Quinn when he used to take bets as to how many you could score against him.
"But standing up in front of 45,000 people and taking one is a different matter. I knew there were better penalty takers than me in that Irish squad so I stayed out of the way and let them get on with it."
However, McCarthy is not planning for a penalty shoot-out.
He added: "We haven't practised penalties and I don't think we will. I don't really see the point to be honest.
"I don't think it will come down to penalties anyway. Spain play an open game. They will create chances and they will give us space to set up chances as well.
"When you look at the attacking talent on the pitch I cannot see this game even going to extra time."
As for his team McCarthy is keeping his cards close to his chest.
"I know the question everyone wants to ask," he said.
"They all want to know if I will drop Ian Harte and play Damien Duff on the left.
"Well, I am not going to tell anyone until Sunday but I know the team I want to play." Spain's coach, Jose Antonio Camacho, believes his side will be up against one of the best teams in the competition on Sunday.
"Ireland are unbeaten against teams like Cameroon and Germany here and Holland and Portugal in qualifying," he said today.
"They can play well at home and away and they know exactly what they're doing.
"Maybe it's a bit early to say but we're talking about one of the best teams here at the moment."
Spain will start as favourites against the Irish after winning all three of their Group B games against Slovenia, Paraguay and South Africa.
Ireland also performed well in the opening round, claiming second place in Group E after beating Saudi Arabia and getting draws against Germany, the group winners, and Cameroon.
Camacho was impressed in those games by Ireland's fighting spirit but he also saw enough quality to suggest his side will face a test of skill as well as of strength.
"The players they have up front aren't there to chase long balls, although the big forward Quinn could come on at the end of needed," said the former Real Madrid player.
"Their style normally is to play the ball around.
"They get into position and play as a block, with six or seven players attacking and eight or nine defending.
"They have a lot of physical strength and they can all attack and defend."
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