And he wants the Socceroos to make him smile again by breaking new ground in Saitama on Tuesday night.
Australia have never beaten the Samurai Blue in Japan, and last claimed a win over them full-stop back in 2009, at the MCG.
But an injured Popovic sat on the bench as Tim Cahill and John Aloisi sealed an incredible 3-1 win in 2006 - Australia's first victory at a World Cup finals.
"Yes, that was a special day, 2006 - I'm still smiling about that as well," Popovic said.Â
"I'm hopeful that tomorrow night, I can be smiling again, but I also understand that Japanese football has improved immensely.Â
"And I know my colleague and friend Moriyasu-san (coach Hajime Moriyasu), has played a big part in that, and credit to him.Â
"They keep growing from strength to strength, and that's something that we have to do as a nation.
"And we need to be challenging Japan for first position every campaign, and we want to have that expectation and that belief, that confidence that we can challenge them."
Happier times: Mark Viduka in action during Australia's 2006 World Cup win over Japan. (Dave Hunt/AAP PHOTOS)
Forward Mitch Duke shook off concerns over a shoulder injury while Aiden O'Neill was the only absentee from training after Popovic's press conference.
There was no reason given for O'Neill as of Monday night - and an update wasn't expected until the Socceroos confirm their squad on Tuesday night.
Moriyasu's Japan have won 20 of their past 22 games, including all three of their round three qualifiers to date - scoring 14 goals across those three victories.
Japan sit top of Group C on nine points with the Socceroos second on four, ahead of Saudi Arabia and Bahrain on goal difference.
The top two teams qualify directly, while third and fourth face another round of qualifiers.
Preparations continue in Japan 🗾— Subway Socceroos (@Socceroos) One final training session - within tomorrow's venue - remains before our @FIFAWorldCup Round 3 qualifier against Samurai Blue 💪 🇯🇵 v 🇦🇺- 15.10.24, 9:35pm AEDT📱💻📺 Paramount+#Socceroos pic.twitter.com/NtHJqGa65OOctober 13, 2024
Popovic and Duke wouldn't be drawn on Australia's record against Japan, while Moriyasu insisted "data doesn't make us win tomorrow's match".
But fresh off beating China 3-1 in Adelaide, there is a newfound confidence.
"We're pleased with the result. We're pleased with the character of the players to come back after being one goal down," Popovic said.
"And tomorrow against a great opponent, great stadium, I want us to have the confidence to build on that performance and to show a better playing style again."
Even a draw would be a sensational result while a win would be among Australia's greatest ever efforts, with the three points crucial for hopes of direct qualification.
"We always believe we can do it," midfielder Jackson Irvine told AAP.
"That's one of the foundations of this team, is the belief we have in each other and the capabilities that we have, especially in the toughest moments.
"And this is a tough moment - we're playing against probably one of the most in-form teams in world football."
Irvine, who wore the captain's armband against China after goalkeeper Mat Ryan was dropped for Joe Gauci, will have a crucial role to play.
Shutting down Liverpool star Wataru Endo and midfield partner Hidemasa Morita will be crucial to determining the outcome.
"These are the moments, and you've got to rise to the biggest challenges and show what you'd be capable of," Irvine said.
Irvine is wary of showing too much respect, too.
"They've got so many different ways to score goals. They've got individual quality, they're good in transition, they've got pace, they've got creativity," he said.
"But we have all of those things as well."
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