Ireland have made four changes for Sunday's clash with Australia at Lansdowne Road.

Ulster winger Andrew Trimble, who was substituted with a tight hamstring in the second half of Saturday's 32-15 victory over South Africa, has lost his fitness battle and is replaced by Denis Hickie.

Hickie, who was drafted into the squad on Sunday as cover, has been handed the number 11 jersey for his 52nd cap while Geordan Murphy replaces Girvan Dempsey at full-back.

Isaac Boss makes his full Test debut with scrum-half Peter Stringer dropping to the bench and his Ulster team-mate Bryan Young also celebrates his first international start, at the expense of loose-head Marcus Horan.

Ireland head coach Eddie O'Sullivan had stated he would experiment with his line-should should South Africa be dispatched in the autumn opener and he remained true to his word, resisting the urge to field his strongest line-up for Australia.

He said: "Andrew Trimble is quite sore. We want to get on top of his injury this week. His hamstring has tightened up and he has spent the week in rehab.

"Andrew could have played but this hamstring problem is ongoing and I want to resolve it as soon as possible, so Denis has come in.

"It was a good result against South Africa and we said we'd look at making some changes.

"Isaac makes his first start at half back and it's an opportunity for him to show what he can do.

"Geordan gets a run at full-back which is tough on Girvan, but I'd like to see Geordan get another run-out.

"In the front row, Bryan Young gets the chance to show what he can do. I was going to put him in at some time this season.

"It's time for him to step up to the plate."

Ireland:  Murphy (Leicester); S Horgan (Leinster), B O'Driscoll (Leinster, capt), G D'Arcy (Leinster), D Hickie (Leinster); R O'Gara (Munster), I Boss (Ulster); B Young (Ulster), R Best (Ulster), J Hayes (Munster), D O'Callaghan (Munster), P O'Connell (Munster), N Best (Ulster), D Wallace (Munster), D Leamy (Munster). Substitutes:F Sheahan (Munster), M Horan (Munster), M O'Kelly (Leinster), S
Easterby (Llanelli Scarlets), P Stringer (Munster), P Wallace (Ulster), G Dempsey (Leinster).