By Chris Roberts, PA Sport

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Former Republic of Ireland international Frank Stapleton has warned Spain that if they underestimate Mick McCarthy's men they will be in for a big surprise.

The Irish discovered today that they will face the Spaniards in the second round of the World Cup in Suwon on Sunday after they secured top spot in Group B with a victory over South Africa.

But if Spain think it will be easy in the next round then the former Manchester United striker believes they are in for a major shock.

"They have played really well," said Stapleton.

"But I'm just hoping they underestimate them (Ireland) and if they do that then they are in for a bit of surprise."

Ireland secured runner-up spot in their group with a convincing 3-0 victory over Saudi Arabia yesterday and will now play in cooler conditions later in the day.

Stapleton feels that will suit the Irish and that they can be the team to bring Spain back down to earth after three opening round victories.

"That's a huge factor," he told Sky Sports News.

"If you can get an evening kick-off it's better for the northern European teams.

"But now we are out of the league stage it's all knock-out and one-off situations and anything can happen. You can just catch somebody cold one day.

"They are playing well and won all of their games so far and they'll be full of confidence, but Ireland are just the team to bring them back down to earth."

The former Arsenal front man has also praised in-form striker Robbie Keane after his two goals, and believes he can go on to break the Irish goalscoring record.

"He's been great and he's still only 21," added Stapleton.

"He's well on his way to taking over the Irish goalscoring record and his contribution to the team is great.

"Maybe it was a blessing in disguise that he hasn't played many games for Leeds since the new year because he looks very fresh.

"He's working his socks off and his understanding with Damien Duff has come from the young international team when they played together.

"That's really working well. He has played up there with Niall Quinn, but whoever he plays with isn't a problem for him. He is very adaptable."

Stapleton now believes McCarthy should stay with the same team that has done so well and keep faith with out of sort Leeds United full-back Ian Harte.

"I wouldn't change anything," he added.

"Probably the one thing that's uncertain is whether Ian Harte will start.

"He has looked a little below par in the last two matches, but it's very hard to change things."