It was almost five years ago that Celtic midfielder Armstrong lined up alongside Robertson for the first time, in a pre-season friendly for Dundee United against German second tier club Union Berlin.
It was hardly the most auspicious of debuts for the then teenage left-back, who had been snapped up from Queen’s Park by United in that summer of 2013. Robertson was substituted at half-time as United lost 4-1 in the picturesque surroundings of the Stadion An der Alten Forsterei.
Yet he still managed to make an instant impression on Armstrong, who will watch with pride when his now international colleague Robertson plays for Liverpool against Real Madrid in Kiev tomorrow night in the highest profile fixture of them all in club football.
“It is quite an incredible achievement for Andy,” said Armstrong. “I watched the semi-final against Roma and sent him a message of congratulations the next day. It is amazing to think that he is going to be walking out in the Champions League final and great to think that he could win it and come home with a medal.
“I can still remember playing my first game with him out in Germany, a pre-season game just after he had joined Dundee United. He was just a young boy, playing left-back with a lot of energy. It is amazing to think now that boy is a Champions League finalist.
“But in that first season at Dundee United, which turned out to be his only season there before he moved south to Hull City, he was what I would call ‘one of one’ anyway. He stood out. You don’t see many players with that level of consistency in Scottish football.
“The thing I love about Andy is that no matter whether he is playing Ross County away or Real Madrid in a Champions League final, he always plays the same way, with the same level of enthusiasm. He has been terrific. I was really proud to see him move to Liverpool last year and now he is a mainstay in that team.”
Robertson’s success at the highest level of English and European club football is an inspiration to his compatriots, such as Armstrong, who are known to harbour ambitions of moving to the Premier League one day.
“Does it prove that other Scottish players can be a success down there?” added Armstrong. “Well, he has certainly showed that he can be a success in that environment, because he has been a major success.”
Armstrong, who has just 12 months remaining on his current contract at Celtic, finished an often frustrating and injury-disrupted season on a high note last Saturday when he appeared as a substitute in the Scottish Cup final victory over Motherwell at Hampden.
The 26-year-old, who has subsequently withdrawn from the Scotland squad for the forthcoming friendlies in Peru and Mexico, is keen to ensure he is back in prime condition to try and reclaim a regular starting place for the double treble winners next season.
“I don’t want to put too much pressure on myself, it is just about making sure I am fit and trying to take my chance when it comes,” said Armstrong. “It isn’t about proving a point. You sometimes take it for granted when you are physically fit and well, and the frustration which comes from being injured. Staying fit and injury free is something I want to be.
“It was nice to come on in the cup final, be involved and be a part of it. We had a fantastic season last season and we’ve been able to repeat that again. Maybe the performances, the fluidity, hasn’t quite been there so much this season but it is very hard to replicate what was obviously an amazing season for us in 2016-17. But when it mattered, we got all three trophies again in the end.
“In January, I was obviously out for an operation, I was out for a couple of months before coming back, so it has been quite a frustrating six months for me. But to be fit again, come on and enjoy the final with the boys, felt great. Playing the tail end of last season, I was struggling physically. To finally get that sorted around January, it took me a while to get back feeling myself, but I’m feeling good now.
“Even last season wasn’t fantastic in every sense for me – people forget I wasn’t in the team until November. That was a different test mentally. Getting my place in the team and having a great season, getting the medals and the accolades and having a short summer, has been testing physically. But that is football. Every boy in this team will have injuries or testing times in their careers and that is how the last six months have gone for me.”