Ireland's quest for the sporting immortality that would come with a first Grand Slam since 1948 continues when they face Scotland in Saturday's Six Nations international here at Murrayfield.

And as if the weight of history didn't weigh heavily enough on Ireland's shoulders, there is also the unwelcome knowledge that the Six Nations usually produces at least one shock result a Championship - and it hasn't happened yet.

Ireland will certainly be huge favourites this weekend but Declan Kidney, their coach, has been warning against the perils of complacency ever since the side kept their bid for a clean sweep on course with a 14-13 win over England.

Almost as additional insurance against those dangers, the former Munster boss has freshened up his starting side for the first time this tournament by making four changes.

Gordon D'Arcy, who a year ago broke his arm in the Six Nations, comes in at inside centre for Paddy Wallace while veteran scrum-half Peter Stringer has ousted Tomas O'Leary after impressing off the bench against England.

In the pack, Denis Leamy takes over from Jamie Heaslip at No.8 while, at hooker, Rory Best starts instead of Jerry Flannery.

Having been out in the cold, or at least among the replacements, the quartet will all be keen to prove their worth.

Talk of a Championship decider away to reigning champions Wales in Cardiff the following week can wait.

Stringer, axed during the 2007 World Cup, said: "I suppose it's fair to say my whole world was rocked when I was dropped. The fear of not being involved in this team is devastating."

The decision of Kidney, in his first Six Nations as Ireland coach, to change things around for this match has also had a salutary effect on those who've retained their places, as lock Donncha O'Callaghan explained.

"When you look at your team-mates you see four guys got bad news, so you know how lucky you are to be involved in it," he said.

"Look at the quality of the players coming in and going out - it shows what a strong squad we have.

"You know when you're given a chance to perform you have to take it."

Scotland went a long way to staving off the threat of the wooden spoon with a 26-6 victory over fellow strugglers Italy at Murrayfield in the third round.

Frank Hadden, their coach, has restored world-class goalkicker Chris Paterson to his starting line-up at full-back while in the second row recalled lock Jim Hamilton will hope to make his 20 stone presence felt after returning from a shoulder injury sustained against France last month.

Hamilton knows disruption of Ireland's set-piece will be vital if Scotland, who were flattered by a woeful Italian side, are to cause an upset.

"Ireland are scrum and lineout-oriented team with two of the best locks in the game - Paul O'Connell and Donncha O'Callaghan."

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