Then, as Melbourne Victory coach six years later, he experienced the Melbourne Storm coach's brilliant intensity in the flesh.
Popovic is famously meticulous, detail-oriented and determined to improve himself and those around him every day.
Sound familiar?
A man who counts Carlo Ancelotti, Jose Mourinho, Pep Guardiola and Guus Hiddink among his influences, Popovic lights up when he, unprompted, brings up one of his biggest inspirations.
"I was fortunate to spend time with Craig Bellamy and you see the work that he's done," Popovic told AAP.
"You talk about meticulous - 
that's what you call meticulous.
"Each pre-season, I'd see him - he's driven to do even better than the last year and thinking about new ways of making the team better.
"That's inspiring for me as well."
Everyone has heard stories of Popovic's gruelling training sessions and expectations that players nail the one-percenters: from eating well to having good sleep routines.
Bellamy isn't surprised to see the "down to earth" Popovic shine with the Socceroos, having seen his mentality first-hand at AAMI Park.
"Obviously when he was at the Victory, from what I could see, he was a really hard worker and he expected high standards," Bellamy told AAP.
"But the thing was that he didn't expect them from his players and not produce that himself - he did. He was big on his standards and what he did and how he did it.
"Out of all the teams and coaches that I've studied and went and visited or whatever, he's right up there at the top of them as to how impressive he was and how passionate he was.
"So I can imagine how passionate he is at the moment with Australia at the World Cup. He's a great guy and a real good coach."
Popovic's work rate is rooted in family, through hard-working Croatian migrant parents.
"Hard work, Christian values, go to church on the weekend, go support your football team after that. I've grown up with that my whole life," Popovic said.
"Then Monday morning, my dad went back to work and working hard to make ends meet and try and make our dreams possible for myself and my sister.
"Obviously it starts from home because you see everyone around you, working hard, enjoying life, happy, not looking for excuses, or (thinking) 'life's tough for me.' You get on with it."
Popovic applied the same approach to his playing career.
"I always had the drive to do the extra and just believe that one day that work will pay off," Popovic said.
"I remember going to the Barcelona Olympics in '92, and I was the youngest member.
"Every morning at 6am, I'd get up and go for a run because I wasn't playing any of the games.
"I'd go for a run with all the boxers along the beach in Barcelona. Then when I played, I felt like I belonged on the field."
Popovic long coveted the Socceroos job, desperate to make his mark on a team that has meant so much to him.
But he didn't expect how the job would change him.
"It's definitely made me better," the 52-year-old said.
"Trying to prepare a team and challenging yourself, can you put it all together in two days, and have everyone on the same page in two days?
"Once I realised that I can do that - it's definitely improved me as a coach, definitely as a leader, in all areas.
"I do pinch myself sometimes. I'm blessed with the greatest job that you can have."
Popovic is adamant the Socceroos can do something special, starting with the opening match against Turkey on Saturday (Sunday AEST).
"I can't wait for the games, because I don't know what I'll be like on the day when we walk out there," Popovic said.
"But I know that the whole country will be behind us, and every Australian living outside of Australia will be behind us and that fills me with a lot of pride."
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