As a fullback Glen Ella was part of the most highly skilled trio of brothers ever to grace a rugby field.

As the Wallabies backs coach, Ella admits he's surprised by the error rate of his butter-fingered charges and estimates they have only been firing at 70 per cent of capacity.

But he feels the glamour Wallabies backline is poised to be expansive, not just expensive, against New Zealand in Saturday's World Cup semi-final at Telstra Stadium.

And Ella hinted they could have some tricks up their sleeve in the form of an "an array of plays we haven't played yet".

The backs have performed well below expectation all year.

Halfback George Gregan's game has come in for renewed criticism, five eighth Stephen Larkham has shown top form only in patches and outside them an ever-changing line-up failed to find attacking rhythm.

To make matters worse, during the Cup tournament the backs have developed an alarming case of the fumbles with fullback Mat Rogers and winger Wendell Sailor the worst offenders.

Ella put the high error rate down to a lack of concentration and skill execution, but believed Australia had the right players to do the job.

"The guys are quality rugby players, they've just got to catch the balls when it's there to be caught," he said.

"I think we haven't achieved the goals we want and the levels we want but I'm sure that the players we are picking have the ability to achieve those levels.

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