Robbie Deans admits the match-hardened Irish represent a massive challenge for his new-look and largely underdone Wallabies outfit on Saturday night.

The Wallabies head into the first of their 15 Tests in 2008 not only with a change of coach and four fresh faces, but also on the back of a bare-bones preparation having only been in camp since last Monday following the completion of the Super 14 tournament.

Ireland, on the other hand, have played six Tests already this year: the Six Nations championship plus last week's torrid 21-11 defeat in New Zealand.

But mindful of Ireland's ambush of the Wallabies when the two teams last met - at Lansdowne Road on the 2006 Spring Tour - Deans said the visitors could not be underestimated.

"I was pretty impressed actually with the Irish (against the All Blacks), particularly their physicality," he said.

"They've developed some frames over the last few years. They're a group that's played a lot of rugby together and particularly in their respective units of up front and out the back.

"They bring with them a lot of mentality, if you like, and it's their last game before a break so they're going to bring everything they've got and they're going to throw everything at us.

"They were pretty impressive around the contact last week and they would also be pretty frustrated by the fact they weren't able to close that gate when it was possibly there to be done.

"So they'll be looking to do that this weekend."

Deans said his selection of Queensland Reds firebrand James Horwill in the second row ahead of in-form NSW Waratah Dean Mumm was to give the Wallabies pack added aggression to combat Ireland's physicality.

"Yeah, James has got that potential in him, there's no doubt, and we're going to need that from everyone," he said.

"We won't be able to back off the physical confrontation and hope to succeed.

"We're going to have to engage Ireland somewhere and we're going to have to do well in that engagement if we're to hope to get home.

"For some (Wallabies), we're going from close to a month since they played rugby at all into a Test match - that's a big step.

"That's a big adjustment. You can talk it all you like but the reality of adapting physically is significant, so that's the first hurdle we've got to overcome."

Wallabies skipper Stirling Mortlock said he was especially excited about once again opposing Ireland and British Lions captain Brian O'Driscoll in a mouth-watering battle of arguably the world's two best outside centres.

"He's a great player," Mortlock said. "You've certainly got to be on your game defensively. He's a very enterprising attacking player.

"And he's a great defender. He rips in at the breakdown, in particular, out wide, so I always look forward to marking Brian."

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