The Wallabies will bring down the curtain on a year that has seen them play 13 Tests when they look to record a third-consecutive Cardiff victory over a Wales side saying farewell to record try-scorer Shane Williams.
While the timing of this two-match trip, which kicked off with last weekend's crushing win over the Barbarians, is less than ideal given it comes hot on the heels of a tough World Cup campaign, Queensland Reds lock Horwill has challenged his side to leave everything on the field before their end-of-season break.
"We are ready to go," he said. "We have a lot of time off and plenty of time to think about it and we want to finish the year on the right note. It has been a big year and we want to make sure going into the break we have good memories of the things we have done here, we are really looking forward to the game.
"We want to finish by winning a Test match and show to ourselves we can play some good rugby and make sure we finish the year well for the group.
"As I said, it's been a big year and we feel we owe it to each other to put in a fine performance that is worthy of the effort put in throughout the year. It is 80 minutes of hard work and then we can have our holidays after that."
The James Bevan Trophy encounter will be Williams' 87th and final appearance for his country, and is sure to be an emotional occasion as the Ospreys finisher heads into international retirement.
And Horwill knows that will make Warren Gatland's side, who are also seeking revenge for their 21-18 defeat in the bronze medal match in New Zealand, dangerous opponents.
"It will get the boys up," he said. "Not only the Welsh crowd but his team-mates will want to send him out on the right note and that is a huge motivator for any group, to do it for a guy that has been such a huge and important part of Welsh rugby and done so much for the game here in Wales.
"They want to send him out on a high and I guess we are here to spoil that party."
Australia, who will have James O'Connor starting at fly-half in a Test for the first time, have been forced into a late change as hamstring injury victim Rob Horne makes way for Anthony Fainga'a in the centre.
But Horwill says the move has not disrupted Wallaby preparations.
He said: "We have a very strong team with combinations from last week, and the whole group has been together since the Tri Nations. Obviously we are disappointed for Rob as his hamstring is not right but Anthony has had opportunities in that 13 jersey and I am sure he will do a fantastic job."
The Millennium Stadium roof will be shut for Saturday's showdown, but Horwill does not feel the atmosphere will prove a problem for his men and believes keeping the elements out could make for a thrilling spectacle.
"It is a new experience for some of the guys," he said. "I played under it when it was shut in 2009 and it adds to the spectacle, the noise gets trapped in.
"It will be a dry pitch and I think it will be good for both teams as they will want a dry, fast pitch for a pretty entertaining game."
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