Five years earlier he had been part of the French squad which beat Uruguay on penalties to win the Under-20 version. Two of his team-mates then – Barcelona defender Samuel Umtiti and Manchester United midfielder Paul Pogba – started against the Croats while another two – Paris St Germain keeper Alphonse Areola and Marseille forward Florian Thauvin – were on the bench.
While he was delighted for his friends, he could not help but feel that he could – and should – have been with them in Moscow’s Luzhniki Stadium.
“I’m still thinking [I could have been there],” he said. “The first thing I did was send them a text to say ‘Congratulations – you won the little World Cup and now you’ve won the big one.’
“I was just like ‘I could’ve been there.’ When you have something in your mind you have to keep it. For me it’s still a goal to be part of the national team and I know it’s going to be difficult.”
Jullien hopes that helping Celtic to maintain their domestic dominance can propel him into national team manager Didier Deschamps’ plans. That he hasn’t been included before now is largely down to his disastrous move to Freiburg immediately after his own World Cup success.
His only appearance for their senior side in three years was as a substitute in a defeat away to Bayern Munich. A loan spell at Dijon led to a £2.5 million move to Toulouse and, ultimately, his £7m move to Celtic on Friday.
Refreshingly, though, he accepts full responsibility for his inability to make a breakthrough in the Bundesliga.
“I am someone who wants to progress every day, so I would say the best time of my career would be the part in Germany… where I failed,” he insisted.
“At the time, I was too comfortable, I was just back from winning the World Cup, I was young and I was maybe thinking that football is easy.
“That bad experience taught me who counts in my life and who can help me to follow my dream. After that, I realised I had to do better.
“It was a difficult and lonely time. I was far from my home in a different country and trying to cope with a different language; it’s different circumstances now because I arrive in Scotland and I’m able to speak English. However, I think every player has to be in a bad position at one point to grow up and learn things. The time in Germany was when I learnt the most. It has definitely made me the man I am now. The coach decided not to play me but maybe it was my own fault.
“I arrived there with the wrong mind-set. I was thinking everything would just automatically be perfect. I thought: ‘I’ve won the World Cup so everything will be fine.’ Then I realised I had to do more. It’s not the name you have or the talent you are born with – you have to work for everything.”