That meant wing Byron McGuigan came into the starting lineup off the bench with Sean Maitland moving into the number 15 jersey, and the former ended as Man of the Match after two tries in what was his first test start.
The late change, and loss of arguably their most influential player in the narrow 22-17 defeat to New Zealand the week before, did not throw the Scots off their game as they showed a willingness to run with the ball and positive intent at every turn.
“We've got good depth just now, Byron McGuigan was outstanding on his first start, and it also says this team are resilient,” Townsend told BBC Sport.
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"They showed that last week against New Zealand when they were dealing with injuries, and dealing with something just before kickoff didn't knock them off their stride.”
For Scotland it is now back-to-back wins over Australia after a 24-19 victory in Sydney in June, while they also claimed a record win against the Wallabies with the most points they have ever scored against a major Southern Hemisphere nation.
"It's an amazing result, to score so many points against the number-three team in the world," Townsend said. "It wasn't perfect, the more the game became unstructured suited us and the fact we had a one-man advantage."
That advantage was handed to Scotland by a deserved red card for Australia prop Sekope Kepu just before halftime that shaped the remainder of the contest, as he barged into a ruck leading with his shoulder and caught the head of Hamish Watson.
"Obviously you have to take into account the red card,” Townsend said. “They were playing well at the beginning of the game, and came back at the start of the second half, but we just kept that mindset of wanting to play and working very hard and it got its rewards."
(Reporting By Nick Said; Editing by Toby Davis)
