Duff - hailed as a star by Irish legend Stapleton.

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Frank Stapleton believes Damien Duff has been the star of the Republic of Ireland's World cup so far after Mick McCarthy's side qualified for the second stage with an historic 3-0 victory over Saudi Arabia.

The former Republic of Ireland striker hailed today's win - the first time the Republic has scored more than one goal in a World Cup game - as a huge boost for the country.

"It has lifted the whole country," said Stapleton, after watching Robbie Keane, Gary Breen and Duff find the net in Yokohama to set up a second round clash with Spain or South Africa on Sunday.

"Duff has had the edge and he has frightened defenders to death.

"I just think he has been the one who was going to be the biggest star for Ireland. The goal was a fluke but he deserved it more than anyone.

"I just always believed they would get through. If they hadn't played very well and got through no one would have cared.

"The Spanish will be worried," he told Sky Sports News.

Former Republic of Ireland captain Andy Townsend believes Ireland have nothing to fear if they end up facing Spain on Sunday.

He said: "They will go into the game as favourites but that suits us.

"We're not expected to win or make the running."

Frank Stapleton also thinks McCarthy's men will not be fazed by the quality of opposition they will face in the next round.

He said: "Ireland are one of the teams no-one wants to meet because they are playing well.

"The Spanish will be very wary because they (Ireland) are an emerging team whose level is going up all the time in terms of world value - they can't underestimate them."

On this performance, Stapleton continued: "The early goal was a blessing - it settled the team down.

"The fear of losing anything from the game was worrying and Saudi Arabia got back into the game but Mick made some changes.

"Niall Quinn came on and it made a difference, and when Gary Breen got the second goal all the nerves went.

"I felt they were going to do it. There's enough confidence in the team and they went about the job properly.

"There were always going to be nerves with so much at stake but they deserved to go through because they've played some wonderful football so far."

Football Association of Ireland chief executive Brendan Menton heaped praise on manager McCarthy after the result and insisted his decision to send Manchester United's inspirational skipper Roy Keane back home was justified.

He said: ``Mick has done a fantastic job and it was a very difficult decision to make as a manager, but there is no doubt now he made the right decision.

``To come through with the African champions going out of the group - which was a group of death - and come through in second place is down to Mick McCarthy and his squad and the way he set out the team.

``It's hot out here, but he's done a fantastic job and we're proud of him and for him. He truly deserves the success that has come.

``It was a fantastic night and a fantastic result. The conditions were probably very humid compared to our first two games - it was a lot more humid here.''

Menton is now looking forward to the likely second stage clash with much-fancied Spain and insists they have no reason to fear anybody.

He added: ``In a one against one knockout situation we won't fear anybody.

``Spain will obviously be favourites, but I think with the spirit in the squad and support we'll get in Korea we don't fear anybody at this stage.''

Former Republic of Ireland and Tottenham centre back Chris Hughton believes the Irish could spring a surprise in their second round match - whoever they face.

The odds are on Spain, who need only a point against South Africa on Wednesday to finish top of Group B and set up a clash against McCarthy's men in Suwon on Sunday.

"Spain will be a difficult game. They are very much the underachievers in European football but they have a wonderful team and on their day they can beat anyone.

"But you can never take anything away from the Irish - they are very much capable of winning."

Hughton was full of praise for the Republic squad after today's victory over Saudi Arabia.

"They went into the game knowing what they had to do and there are no easy games - the Germany result (8-0) was very much a one-off against Saudi," he told Sky Sports News.

"The Republic scored the early goal, which was of great benefit and after that it was a very, very good performance.

"It is difficult to dominate a game for 90 minutes and once Saudi conceded the early goal they had to get better and there was going to be a period where they (Ireland) couldn't dominate but what they didn't do was concede.

"It is a wonderful day for the team. A lot of people forget the qualifying group they came out of. It was a very difficult group, then they had to go to a play-off so nothing surprises me about this team.

"They have a lot of spirit and a lot of quality and I would like to see them go as far as possible."