After their previous disappointing showing against Japan, the head coach told his Irish squad to improve their game.
The team responded immediately.
The Irish side had faded late against New Zealand and required considerable time to find their rhythm versus their Asian opponents.
However, against Australia, they started powerfully, with the talented back excelling brightest during a 46-19 victory that represented Ireland's best performance of the season.
Making his first test match start at full-back, Hansen registered a three tries, competed excellently for high balls and performed outstandingly against the nation of his origin.
"You know, I've had a pretty challenging run with fitness issues honestly," the athlete stated.
"I missed being in this squad, I understand there's much talk about me not necessarily being born here and I didn't grow up here, but I love this team and this feels like home.
"Any time I have to play for the national team it's a privilege, if you fail to deliver a good showing you might not get that privilege again.
"My entire focus this period was to take the field and do what I can do."
After 28 caps on the flank, Hansen was entrusted the full-back position for the initial time with multiple players injured.
In his case, it was simply a matter of continuing where he finished during the warmer months.
The experienced player had been in superb form before physical issues ended his dream of making the Test team.
Having come back recently, he suffered a foot injury that made him unavailable for previous matches.
Farrell had indicated that the player was especially motivated and these proved not hollow words as the former club player gave his coach a welcome team dilemma for future games.
"So my initial thoughts were, 'You better play well in those two colored boots!'," said Farrell, alluding to Hansen's decision to sport different footwear.
"In fact I thought that was fitting but apparently Mack just made that personally anyway. So he's drawn notice to himself before he's even begun.
"I told to him before the match, 'Excellent players don't need justifications, they can perform and just play naturally, you can win the player of the game if you want,' and he responded, 'Yeah, I concur.'
"Therefore he's that type of player, he trains thoroughly, he's got a great attitude to understand his detail and so that's why he fitted straight into the team and he was able to perform naturally due to that."
Hansen's efforts also earned commendation from the rival coach, who remarked he was the "standout opposition player" on the night.
"I thought he was outstanding, his experience showed to the front," said the former international coach.
"Regrettably, Hansen was probably the standout opposition performer on the field. He's has a excellent skillset and he's such a strong contender."
When asked about what enables the player a good option at full-back, Farrell continued: "Appearing in the center of the pitch is something that he does from the wing anyway, but I suppose he's more in place for that frequently.
"His aerial play was excellent, don't you think? I believed we didn't get bored of executing the correct thing and that was placing the possession back on them to secure field position.
"Why that was the correct strategy to do is because it's the players of Mackie who was securing the possessions back, and additional teammates, so [it's] quite satisfying."
Outside the star performer, there were multiple encouraging aspects for the coach.
Sam Prendergast was excellent on his comeback to the number 10 jersey, the set piece and line-out functioned smoothly and different player did not look uncomfortable in his debut start in the front row.
But perhaps most pleasing for Farrell was the team framing the match with multiple strong periods.
The player's initial couple of scores came in the first 11 minutes while additional players registered in the final exchanges after the other team had crossed, ensuring the Irish side finished on a positive note.
"In my opinion we truly let ourselves go and attacked the game straight from the word go," said the coach.
"The way we handled numerous elements throughout the game, especially them coming back just before the break and reorganizing ourselves and giving a display like we did in the later stages, I thought as far as territory and being across most of our game in that later period was really satisfying."
The strength of the Springboks are awaiting for Ireland, in what might be considered as an informal conclusion to the previous season's drawn multiple match series on rival soil.
The coach's team will require to attain a higher level to defeat the back-to-back title holders, but Saturday's defeat of the Australian team was a significant step in the correct path after an uninspiring start to their autumn schedule.
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