After their previous underwhelming showing against Japan, the head coach challenged his Ireland squad to step up their game.
The team responded right away.
The Irish side had faded in the final stages against New Zealand and required most of the match to find their rhythm versus Japan.
Nevertheless, facing Australia, they started strongly, with the talented back excelling most prominently during a 46-19 victory that represented the team's finest performance of the season.
In his debut test match start at the number 15 position, the player registered a hat-trick, competed brilliantly for high balls and performed outstandingly against the nation of his origin.
"Look, I've experienced a pretty difficult period with injuries really," the athlete commented.
"I missed being in this team, I understand there's much talk about me not necessarily being raised here and I wasn't raised here, but I adore this team and this feels like family.
"Any time I get to represent for Ireland it's a honor, if you fail to deliver a good showing you may not get that opportunity again.
"My entire focus this week was to take the field and perform what I can do."
After twenty-eight appearances on the wing, the player was given the number 15 position for the first time with several players unavailable.
In his case, it was essentially a matter of picking up where he left off during the summer.
The 28-year-old had been in excellent form before injury ended his aspiration of joining the Test squad.
After returned last month, he suffered a lower body injury that ruled him out for previous fixtures.
The coach had indicated that Hansen was particularly motivated and these proved not empty statements as the former provincial player gave his coach a welcome team headache for future games.
"Well my first thoughts were, 'You better play well in those two coloured boots!'," commented Farrell, alluding to Hansen's decision to sport different footwear.
"Actually I believed that was fitting but it seems Mack just did that personally regardless. So he's drawn attention to himself before he's even started.
"I said to him before the game, 'Good players require no excuses, they can perform and just play naturally, you can get the player of the game if you choose,' and he went, 'Yes, I agree.'
"So he's that type of performer, he trains thoroughly, he's has a great attitude to understand his preparation and thus that's why he slotted right into the team and he was able to be himself due to that."
The player's efforts also received praise from the rival coach, who remarked he was the "exceptional opposition performer" on the evening.
"I thought he was outstanding, his knowledge was evident to the front," commented the ex- national coach.
"Unfortunately, Hansen was likely the standout Australian player on the pitch. He's has a great ability and he's such a strong competitor."
Pressed about what enables Hansen a good option at the number 15 position, Farrell continued: "Appearing in the middle of the pitch is something that he demonstrates from the wing anyway, but I imagine he's better in position for that frequently.
"The player's aerial play was brilliant, wasn't it? I believed we persisted of executing the right thing and that was placing the possession again on them to secure territory.
"The reason that was the correct thing to do is since it's the likes of Hansen who was getting the possessions back, and other teammates, so [it's] quite satisfying."
Outside the star performer, there were numerous positives for the coach.
Another player was excellent on his return to the number 10 position, the scrum and line-out functioned effectively and different player did not look out of place in his first appearance in the front row.
But possibly more pleasing for the manager was the team framing the match with two strong spells.
Hansen's initial couple of tries came in the opening 11 moments while additional teammates registered in the closing stages after the other team had crossed, guaranteeing the Irish team finished on a high.
"I thought we truly let ourselves go and attacked the game right from the word go," stated the coach.
"How we handled numerous aspects during the match, especially them responding just before half-time and regathering ourselves and giving a display like we achieved in the second half, I believed as far as territory and being across the majority of our game in that later period was truly satisfying."
The strength of the Springboks are awaiting for Ireland, in what might be considered as an informal decider to last year's drawn multiple match series on rival territory.
Farrell's side will require to attain a higher standard to defeat the consecutive world champions, but Saturday's victory of the Wallabies was a important step in the right direction after an uninspiring start to their autumn schedule.
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