"I don't have any answers as to why. If I did, you would probably have seen it out there.
"But you can see the game actually tighten up towards the end there, so whether that's teams being aware of the situation, I'm not sure."
The Wallabies have been worked hard in training under Cheika but players insist fatigue is not playing a part.
Australia will be able to leave everything on the pitch against England at Twickenham on Sunday in their last test of the season.
England inflicted the Wallabies' only loss of last year's tour and Toomua -- who looks certain to retain his starting spot -- admitted memories of the 20-13 loss 12 months ago would serve as motivation.
"It was probably the loss that hurt us most last year," he said. "We won't be short of motivation but you never are at international level."
Australia need to avoid defeat to prevent their worst European campaign since 2005.
"Three losses in a row to finish the year wouldn't be great but we're doing a lot of hard work and a lot of right things so we know we're moving forward and we'll start getting the results," Toomua said.
"Hopefully, that starts this week but you definitely want to finish the year with a win."
- AAP