Callam is looking forward to his first Scotland start

Hadden makes two changes following last weekend's victory over the Pacific Islanders in the second autumn Test.

Callam replaces the injured Johnnie Beattie at number eight.

Mike Blair starts at scrum-half in place of Chris Cusiter, who was also taken off injured during the 34-22 victory on Saturday.

News conference: Scotland coach Frank Hadden

Callam anticipates first start for Scotland

The 23-year-old Callam was a replacement for that game and the opening Test win over Romania and was among the try-scorers last weekend.

"Dave Callam certainly took his opportunity last week when he came on as a replacement, and there wasn't really any discussion at all about him starting," said Hadden.

"While David has not come through as rapidly as we had hoped, a lot of that was down to a lack of opportunities."

But injuries to captain Jason White, Allister Hogg and Beattie sees Callam get his chance.

Scotland head coach Hadden is hoping his team can maintain their winning home record in 2006.

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"We are unbeaten at Murrayfield this year and everyone involved with the squad is proud of that," he said.

"We will require a top-drawer performance from our entire 22 to maintain that on Saturday."

Glasgow Warriors stand-off Dan Parks keeps his place in the starting XV against the Wallabies.

Rory Lawson and Alasdair Strokosch start on the bench as they join a senior Scotland squad for the first time.

And Hadden expects both men to come off the Murrayfield bench at some point.

He said: "In all the games I've been involved in with Scotland, we have only left someone sitting on the bench a couple of times.

"It's not just about the starting XV. It is very much a 22-man game these days, and it is important we have players who can make a genuine impact when they come off the bench."