Australia, hardened by playing in a Rugby Championship dominated by world champions New Zealand, overwhelmed Wales 32-8 in Cardiff last weekend.
Wales were badly off the pace in their opening end-of-year Test and this weekend sees Scotland start their November international campaign in their first meeting with Australia since last year's agonising 35-34 World Cup quarter-final loss to the Wallabies at Twickenham.
Back-row forward Barclay had a particular insight into Wales's mood as he plays his club rugby for the Llanelli-based Scarlets, a Welsh regional side.
"You could maybe tell Australia had played a lot recently and Wales hadn't played together as a unit but that's something we have to learn from," he said Wednesday. "It's important we don't fall into that trap as well."
Barclay, who was in touch with a some of his club colleagues after their heavy loss, added: "I exchanged a few text messages here and there.
"They were bitterly disappointed so you don't want to pry too deep. But you can see a lot from the video where they went wrong.
"One of the main differences is the speed everything happens at. They were trying to get forward and Wales have had a great defence in recent years.
"But Australia played a lot of options inside and outside, it's obviously something they looked at before the game and it all came off for them.
"Certainly they want to play fast ball, they want to play with the ball in front of them, moving the ball. Every team's goal in defence is to slow it down, if not turn it over, so nothing changes there really."
But the 30-year-old former Glasgow loose forward said the Wallabies posed a specific threat.
"They attack slightly differently, they have a lot of trail plays, a lot of movement, a lot of multiple-option plays, where defenders around the ball have all got to be doing the right job, not just the guy in front of the ball," Barclay explained.
"So, yeah, they present a unique challenge, but I believe defence is relatively straightforward.
"But the speed of how it happens in international rugby, you don't have the recovery time that you maybe do in a pro rugby game."
Barclay missed the World Cup clash against Australia -- a side he has twice enjoyed wins over in his two previous encounters with the Wallabies -- after a near two-year period of international exile ended with last season's Six Nations.
"I kept my head down for a couple of years and got my chance to come back in," he said. "It does make you more hungry to get back in and stay there.
"When you play in Scotland you are in and around the coaches and the environment more than you are out of the country."