Brian O'Driscoll received most of the plaudits, but Ireland's captain credited an unsung Australian as largely responsible for his last-gasp try that crushed the Wallabies' grand slam hopes.

O'Driscoll wasn't talking about Quade Cooper or Digby Ioane either, after surging through a gaping hole between the Wallabies' inexperienced centre pair to clinch the 20-20 draw at Dublin's Croke Park on Sunday.

No, Ireland's superstar centre paid tribute to the rugby smarts of former Randwick player and coach Alan Gaffney - a one-time Wallabies assistant to Eddie Jones - for plotting the brilliantly-executed set move that served as a dagger to Australia's heart.

From a scrum win five metres out from the Australia line, and with a minute left on the clock, halfback Tomas O'Leary picked out O'Driscoll from a wave of Ireland attackers running in all directions to leave the Wallabies midfield defence completely bamboozled.

The straight run untouched for a try gave O'Driscoll, the highest-scoring centre in international rugby history, a spectacular conclusion to his 100th Test match.

"Some of the kudos needs to go to Riff (Gaffney). He would have had a huge impact," O'Driscoll said of the Irish backs coach.

"He's a great rugby brain and he thinks a lot about how to break down teams. It's nice when plays like that come off.

"It's a smart play. We've practised it a hell of a lot over the last year. Even during the Six Nations, we didn't have an opportunity to do it.

"In training, it's had good effect but the real test is playing in Test matches and it did open up for us."

The try was Ioane's worst nightmare realised.

Playing just his second Test at outside centre - the most difficult defensive position in the backline - Ioane spoke pre-game about how he feared his deadly opposite O'Driscoll beating him to score.

Post-game, a dejected Ioane said "O'Driscoll just ran a good line and the (blind) winger (Keith Earls) ran a good decoy", while Wallabies coach Robbie Deans lamented how "that's what pressure does - it creates doubt."

Five-eighth Matt Giteau complained that Ireland would never have scored the try if referee Jonathan Kaplan had penalised O'Leary for not feeding the ball quickly enough as Australia's dominant forwards had the Ireland's scrum reeling.

"Then next time the ref asked him to put it in and we didn't feel that feed was quite straight," Giteau said.

"That's just making excuses, I suppose. Once we got to that lead, we should have held onto it.

"And, as a unit, we probably didn't defend as we should have. When they go to the line, as a side we all need to jam and take a man."

Brought to you by AAP © 2024 AAP