Halfback Genia was undergoing surgery on a broken arm on Sunday as the Wallabies flew to Sydney for Saturday's sold-out third Test, keenly aware of the enormity of their task following the 26-21 second Test loss in Melbourne.

Ireland showed why they are ranked world No.2 as they upped the ante with a full-strength team, having rested or benched several key players for the first Test in Brisbane.

The scoreline flattered the Wallabies, who played with just 35 per cent possession and succumbed to ill-discipline - giving up 15 penalties and a costly yellow card to winger Marika Koribete - as they struggled to cope with the accuracy of the Irish.

Notably it was Genia who called them together and reasserted order after the early pressure but his broken arm suffered shortly after was a cruel blow and he is unlikely to play again before the Rugby Championship in August.

Wallabies coach Michael Cheika claimed post-match that Genia had been "king-hit" off the ball by Cian Healy's shoulder, although the Irish prop has not been cited.

Five eighth Bernard Foley acknowledged the significance of Genia's loss.

"Will has got a great understanding of the game and can control the game exceptionally well through his running, his kicking and his passing," said Foley.

However he backed seasoned deputy half Nick Phipps and likely new back up Joe Powell.

"I have a lot of faith in Nick and what he's bringing," Foley said. "There will be small adjustments but nothing too significant that's going to change the way we're going to play."

There was some good news for the Wallabies on Sunday, as scans cleared lock Adam Coleman of a fractured cheekbone.

With playmaker Johnny Sexton back calling the shots, Ireland did a great job of nullifying the Wallabies' strengths from the first Test, including winning the breakdown, where David Pocock had reigned supreme.

The Wallabies' kicking game, so useful in game one, was wayward and ineffective in Melbourne and danger man Israel Folau was closely marked.

Foley believed Australia had the right tactics but just didn't execute well enough.

"We knew there was going to be a significant step up but it didn't change how we approached the game," Foley said.

Prop Scott Sio admitted the Wallabies assisted in their own defeat but believed there were also promising signs.

"Discipline let us down, especially in that first half," Sio said on Sunday.

"We can't be playing with 35 per cent possession ... the territory and possession game is pretty key at Test level, so I think we just need to treasure the ball a bit more.

"We need to be better with our kicking and just be a lot more clinical around the park with everything we do.

"Even with the territory and possession battle going against us we still gave ourselves a shot at the end to win the game.

"Scoring three tries to two is definitely a positive with so little possession."

Foley believed the Wallabies would be well and truly up for the third Test.

"We would have liked to have sealed it up in two but it's now something we have to embrace," he said.

"It's excitement - you don't get too many challenges like this. It's like a grand final."

Australian Associated Press