Centre Ashley-Cooper's try gave the Wallabies their slim lead with minutes remaining in the match at Docklands Stadium, though the Lions had the opportunity to snatch it with a last-minute Leigh Halfpenny penalty attempt that fell just short.
"I think we've got a lot more in us, I thought the game (on Saturday) wasn't of great standard," the 29-year-old told reporters in Sydney on Monday.
"We made a lot of improvements from game one (which the Lions won 23-21), but we certainly feel we've got a lot more improvements to make."
Ashley-Cooper's summation of the game was not out of step with many observers, who felt the match had not been of the standard expected of the occasion.
Former England and Lions coach Clive Woodward wrote in his column that he felt the game was poor while British columnist Mark Reason, who now lives in New Zealand, labelled the Australia side as the 'Dullabies' and their tactics 'turgid'.
Ashley-Cooper recognised the Wallabies had not used their attacking threat in wingers Israel Folau and Joe Tomane as well as they should have and they would be working on that as they prepared for the final match on Saturday.
"I think for us a lot of improvement can be made in the backs," Ashley-Cooper added. "Possession was a bit of a issue. We need to hold onto the ball more.
"We've got too many threats in the backline to waste, so we're hoping to get the ball into the wider channels this week."