The Wallabies are on alert to ensure ill-discipline is not a result of their desire to hand Japan a heavy defeat in their World Cup opener on Saturday.

Captain Stirling Mortlock admits the 30-strong contingent is "on edge" at the end of seven weeks' training, in which they have not played a game.

"You can only take so much training," he said. "The guys are certainly on edge. That is a good thing, and everyone has good head space."

The Wallabies realise they must harness the building enthusiasm and not let it cloud their on-field judgement. Besides the risk of costly penalties and yellow cards, repeated on-field offences could lead to red cards and suspensions for other Cup fixtures.

That, admits Mortlock, is a hazard in the pool rounds, where minnows, such as Japan, may seek to frustrate their more-fancied opponents into giving away penalties to make up for their physical and tactical deficiencies.

"Discipline no doubt [is something] the team will be addressing," he said. "Whether they [the opposition] are ranked in the top three in the world or in the back end of this tournament, they are still going to go out there with best intentions and likely stiffen a few guys up.

"It is all about a very solid mental approach, sticking to our game plan and being very disciplined about how we go about our business."

Mortlock expects discipline to be more closely marked by referees than ever in this World Cup.

That is an understandable concern, considering his admission that in recent years - in non-World Cup seasons - the Wallabies have been caught out for letting referees' scrutiny get the better of them. "It's something referees are looking at probably tightening up on in the World Cup," Mortlock said. "Over the last year or two, in some stages our momentum has been stifled by poor discipline. So, that will be a focus for this team …"

The Wallabies forwards are especially wary of letting emotions get the better of them in the battle up front.

"Obviously it is a bit hard discipline-wise, first game," loose-head prop Matt Dunning said. "Everybody is going to want to get out there. But hopefully we can channel all that enthusiasm into a positive"

Al Baxter, the Wallabies' starting tight-head prop, agrees. "Everyone is raring to go, just busting to get out there." he said. "[But] over-enthusiasm in a big match can be very detrimental, [especially] if you give away soft penalties in the first few minutes and they get points."

However, Baxter believes the danger in their first game would be greater if the Wallabies were playing a tougher opponent.

"We are going to have to play well [against Japan]. But if we were playing Wales or one of the big teams early, it would be a lot harder," he said.