After their previous disappointing showing against the Japanese team, the head coach challenged his Ireland team to step up their performance.
The team responded immediately.
Ireland had faded in the final stages against New Zealand and taken most of the match to find their rhythm versus their Asian opponents.
However, facing the Wallabies, they began powerfully, with the talented back shining brightest during a comprehensive triumph that marked the team's best performance of the season.
Making his debut test match start at full-back, Hansen scored a three tries, contested excellently for high balls and played exceptionally against the nation of his birth.
"Look, I've had a pretty difficult run with injuries honestly," Hansen stated.
"I missed being in this squad, I know there's considerable talk about me not necessarily being born here and I didn't grow up here, but I love this group and this seems like family.
"Whenever I get to represent for Ireland it's a honor, if you don't put in a performance you may not get that privilege again.
"My entire approach this week was to go out and do what I can do."
Following twenty-eight caps on the flank, Hansen was entrusted the number 15 role for the first time with several teammates injured.
For him, it was essentially a matter of picking up where he finished during the warmer months.
The experienced player had been in excellent condition before injury disrupted his dream of joining the Test squad.
After come back last month, he developed a lower body problem that made him unavailable for earlier matches.
Farrell had indicated that Hansen was particularly determined and these turned out to be not hollow words as the former provincial player gave his coach a positive team headache for future matches.
"So my first thoughts were, 'You need to play well in those two coloured shoes!'," commented the coach, referring to Hansen's decision to wear mismatched boots.
"Actually I thought that was fitting but it seems Hansen just made that personally regardless. So he's drawn notice to himself before he's even begun.
"I said to him before the game, 'Excellent athletes require no justifications, they can perform and just play naturally, you can win the man of the match if you choose,' and he went, 'Yeah, I concur.'
"Therefore he's that kind of player, he prepares thoroughly, he's has a great approach to get across his preparation and so that's why he fitted right into the team and he was able to perform naturally because of that."
Hansen's performance also earned praise from the opposing manager, who remarked he was the "standout opposition player" on the evening.
"I thought he was super, his knowledge showed to the front," said the ex- national manager.
"Unfortunately, Hansen was probably the standout Australian performer on the field. He's got a great skillset and he's such a good competitor."
When asked about what enables Hansen a good fit at full-back, Farrell added: "Appearing in the center of the pitch is something that he does from the flank anyway, but I suppose he's better in position for that frequently.
"His aerial play was brilliant, wasn't it? I thought we persisted of doing the right approach and that was placing the ball back on them to secure territory.
"The reason that was the correct strategy to do is since it's the likes of Hansen who was securing the possessions back, and additional players, so [it's] quite pleasing."
Beyond Hansen, there were multiple encouraging aspects for the coach.
Sam Prendergast was excellent on his comeback to the fly-half jersey, the scrum and throw-in operated smoothly and another teammate did not look out of place in his first start in the front row.
But perhaps most satisfying for Farrell was Ireland framing the game with multiple strong periods.
Hansen's first couple of tries occurred in the opening eleven minutes while other players registered in the closing exchanges after the opposition had scored, ensuring the Irish team finished on a high.
"In my opinion we really performed freely and approached the game right from the beginning," stated the coach.
"The way we handled numerous aspects during the game, particularly them responding just before half-time and reorganizing ourselves and giving a display like we did in the later stages, I believed as far as field position and being familiar with the majority of our game in that later period was really satisfying."
The strength of South Africa are awaiting for the team, in what could be considered as an informal decider to the previous season's drawn two-Test contest on opposition soil.
Farrell's side will require to reach a higher level to defeat the consecutive world champions, but the recent victory of the Australian team was a important advancement in the right direction after an disappointing beginning to their fall campaign.
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