Following their previous disappointing showing against Japan, the head coach told his Ireland team to improve their game.
Ireland responded immediately.
The Irish side had faded late against the All Blacks and taken considerable time to get going versus Japan.
Nevertheless, against Australia, they started powerfully, with the talented back excelling brightest during a 46-19 triumph that represented Ireland's finest performance this year.
Making his first international appearance at full-back, Hansen scored a three tries, competed brilliantly for high balls and played outstandingly against the nation of his birth.
"You know, I've had a pretty challenging period with fitness issues really," Hansen stated.
"I longed for being in this team, I know there's considerable talk about me not exactly being raised here and I wasn't raised here, but I love this team and this feels like family.
"Any time I get to represent for the national team it's a privilege, if you don't put in a good showing you may not get that privilege again.
"My whole approach this period was to take the field and do what I could do."
After twenty-eight caps on the wing, Hansen was entrusted the number 15 role for the first time with several teammates injured.
For him, it was simply a matter of picking up where he left off during the summer.
The 28-year-old had been in excellent form before physical issues ended his dream of joining the Test team.
After come back last month, he developed a lower body problem that made him unavailable for previous fixtures.
The coach had indicated that Hansen was especially motivated and these proved not empty words as the ex- club player gave his coach a welcome team headache for future games.
"Well my first thoughts were, 'You need to play excellently in those two coloured boots!'," commented Farrell, alluding to the player's choice to wear different footwear.
"In fact I thought that was fitting but apparently Hansen just made that himself anyway. So he's attracted notice to himself before he's even started.
"I told to him before the game, 'Excellent athletes don't need justifications, they can get on with it and just be themselves, you can get the man of the match if you choose,' and he responded, 'Yes, I agree.'
"Therefore he's that kind of player, he trains well, he's has a excellent attitude to get across his preparation and so that's why he slotted straight into the team and he was capable to be himself due to that."
The player's efforts also received commendation from the opposing manager, who remarked he was the "exceptional Australian player" on the night.
"I thought he was super, his experience showed to the front," said the former international manager.
"Unfortunately, Hansen was probably the best Australian performer on the pitch. He's has a great ability and he's such a good contender."
Pressed about what makes Hansen a good option at full-back, Farrell added: "Showing up in the center of the pitch is something that he does from the flank regardless, but I imagine he's more in position for that more often.
"His aerial work was brilliant, wasn't it? I thought we didn't get bored of doing the correct approach and that was putting the ball back on them to gain territory.
"The reason that was the correct thing to do is since it's the likes of Mackie who was getting the possessions returned, and other teammates, so [it's] quite pleasing."
Outside the star performer, there were numerous encouraging aspects for Farrell.
Sam Prendergast was excellent on his return to the number 10 jersey, the scrum and line-out functioned effectively and different player did not appear uncomfortable in his first start in the forwards.
But possibly more satisfying for the manager was the team framing the match with multiple strong periods.
The player's initial two tries occurred in the first 11 minutes while other teammates scored in the closing exchanges after the opposition had crossed, ensuring the home side finished on a positive note.
"I thought we truly let ourselves go and approached the match right from the beginning," stated the coach.
"The way we managed various elements during the match, particularly them coming back just before the break and reorganizing ourselves and producing a display like we achieved in the second half, I thought as far as field position and being across most of our game in that second half was truly pleasing."
The strength of South Africa are awaiting for the team, in what could be viewed as an unofficial decider to last year's drawn multiple match contest on opposition soil.
The coach's side will require to attain a higher level to defeat the back-to-back title holders, but Saturday's victory of the Wallabies was a significant advancement in the right direction after an uninspiring start to their fall campaign.
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