Australia coach Michael Cheika scolded Will Skelton for picking up a needless yellow card in the closing stages of the 23-22 victory over Scotland at Murrayfield.
The Wallabies were trailing 22-16 when lock Skelton shoulder charged Jonny Gray in the 69th minute, with the referee sending him to the sin bin and overturning a penalty which had been awarded to the visitors.
Cheika's men still managed to grind out a win, with Bernard Foley converting Tevita Kuridrani's try, but the coach lamented Skelton's lack of discipline under pressure.
"He's got to put his arms around that guy and he knows that. It's ill-disciplined from him," said Cheika. "Those decisions come down to the ref - whether it's a penalty or a yellow - but regardless it's an offence.
"We had our own penalty, it's after the whistle and it wasn't clever. He knows that himself. I don't even need to tell him so I don't think he'll be worried about me saying it here."
Cheika felt the Wallabies lacked focus but believes a stronger mentality is being forged after series defeats to England and New Zealand.
"You'd like to think a game like that would give you a bit of belief that that's happening. I think it is," he added.
"The reason I say that is because I see it in the line speed in defence, which is standard at this level.
"I always back my blokes. They are learning about that stuff, about how to stay in the contest and not have to have all the play perfect."
Scotland boss Vern Cotter bemoaned his team's lack of luck during the second half as Australia battled to victory, just as they did when the teams last met in the 2015 Rugby World Cup quarter-finals.
"We'll always come back to the old saying of fine margins. I wouldn't necessarily say the best team won," said Cotter.
"I'm incredibly proud of the way the players played that game. There are things we can and can't control and we'll focus on the things we can.
"I just think we didn't get the rub of the green at times. I thought the team adapted well to injuries and it might have just come down to - I've got to be careful what I say.
"There were eight penalties against us in the second half and only two for us; there were a number of things. But that is something we can't focus on."