Since then, the 19-year-old has got niggly with Neymar in the Champions League, signed a bumper new deal, suffered a serious knee injury and gone on loan to Dundee United.
Now he is ready to go full circle on Wednesday when Scot Gemmill’s side face another semi-final against England in Aubagne.
A year ago, Ralston, left, was lining up in the Stade Parsemain facing England in the semi-finals, which the Scots lost 3-0. That was to kick-start a roller coaster year for Ralston, who went toe-to-toe with Brazilian PSG superstar Neymar and laughed in his face. However, the ex-Barcelona genius had the last laugh in a 5-0 Parkhead win.
Ralston then signed a four-and-a-half year deal in December, had to undergo surgery with a knee operation before ending the season on loan at Dundee United. And he insists he has loved the ups and downs of the season.
He said: “It’s crazy to think of the things that have happened since that England game. It’s been quite mental, but unreal at the same time. I feel I’ve grown as a player over the past year. In a way it all started with playing in this tournament. It’s been ups and downs. From the start of the season, living the dream as a Celtic fan playing for the first team. Then my injury and dealing with that, then going out on loan and enjoying the games I played in.
“Celtic have been unreal this season. I’m immensely proud to have been a part of that as well. But I enjoyed my time at Dundee United and they were very good with me. Getting the experience of dealing with an injury – a serious one – and having an operation was all new. It’s about how you deal with the downside and enjoying the ups. It’s been a good season overall and one to remember.
“I always look back on the Champions League night against PSG as a positive night. It’s all about experiences and playing against that calibre of player is only going to give me the confidence to go up against any player.
“Neymar is a very talented footballer and one of the best in the world. I still take great confidence from that night going into every game. I enjoyed the challenge, it’s the thing I grew up as a kid dreaming of doing. There were 60,000 there on a Champions League night and I’m honoured to say I’ve done it.
“It’ll stick with me forever. I wouldn’t change any of it.”
Ralston is looking forward to returning to Parkhead to challenge for his place next season. He said: “I’m not looking too far ahead. I’m focusing on doing well here for my country. It’s a massive part of my career too.
“Going back into Celtic I’ll be hoping to push and show I can get in the team. That will be my main aim.
“If things don’t work out I’ll just have to see how things go. I’m looking forward to getting back in for pre-season, getting my head down and working again.”