An unused substitute for the Under-21s that very afternoon against Croatia, he knew he had significant work to do to convince not only Steve Clarke that he was worth considering, but also, in the first instance, Neil Lennon, his then manager at Celtic.
As had to be expected given he was just 21-years-old, he was required to bide his time in terms of starts following his belated move from Motherwell. He was being more often used as a late substitute.
That didn’t stop him dreaming, however. As well as Turnbull, three others in the Scotland squad for that 2-2 draw at Tynecastle have since gone onto play for the full international side. Indeed, two of them might now be considered mainstays. Not only did Nathan Patterson and Billy Gilmour join Turnbull in being named in Clarke’s 26-man squad for the Euros, but they actually enjoyed some game-time.
Although he's pushing for a place now, Turnbull had to be content with a watching brief as Scotland were eliminated at the group stage in the summer. Lewis Ferguson, who started in midfield for Scot Gemmill's side against Croatia, has also since been called up. It’s proof that the Under-21 team is performing precisely as it should in fulfilling the role of stepping stone to the full international side.
A year on from watching Scotland clinch a place at a major finals and enjoying all the subsequent celebration clips on social media, Turnbull hopes to contribute to securing another play-off place against Moldova on Friday. Even for those tuning in from Scotland, which was pretty much everyone due to Covid restrictions barring any travelling supporters, the memories of a night of nights in Belgrade remain vivid. Turnbull watched the drama unfold in a hotel in Edinburgh.
“It was a good night that,” he said. “I was away with the Under-21s at that point and me and a few of the boys sat in one of our rooms and watched it. We had had a game that afternoon. Lewis Ferguson was one of them. We were actually speaking about whether there was an opportunity there for us.
"We said: ‘we will just need to wait and see what happens’. I am not sure that any of us thought we would. To get the opportunity to be in the squad after that has been great.”
Turnbull is now seeking to establish himself in the Scotland side the way he has at Celtic, where he has become an integral member of Ange Postecoglou’s side. He has made 25 appearances already this season after slipping in and out of the side under Lennon.
“It took a while but I got there in the end,” he admitted, with reference to making a sustained first-team breakthrough. “Now it’s just about working as hard as I can here with Scotland and just hoping and waiting for my chance.
"Hopefully I can take it whenever it comes. That’s what I’m looking to do.”
He should be feeling ever more at home amongst seasoned internationalists and judging from his form for Celtic – he was one of the standouts in Sunday’s 4-2 win over Dundee – he certainly merits his place in the squad.
Asked if that was the case, he said he was “maybe a little” more comfortable in such a setting. The familiar surroundings of La Finca resort in Alicante should help. This is where he met up with his full international teammates for the first time before making his debut in the 2-2 Euro 2020 warm-up draw with the Netherlands in Portugal. Scotland have headed to the Costa Blanca once again to prepare for the forthcoming doubleheader, which sees Scotland host Denmark three days after the trip to Chisinau.
“The first time I got called up was in the summer and at that stage it was just about trying to get to know the boys,” Turnbull recalled. “I loved every minute of that. Just to get picked was a big thing. Every camp since has been about pushing on and now I feel more part of the squad.
“All the boys have been brilliant with me and now it’s about continuing that,” he added.
There’s every chance he will be involved in Chisinau. He appeared as a late substitute in the 1-0 win over Moldova at Hampden in September to win his third full international cap. He knows that the opposition cannot be discounted, particularly when they are playing at home. It took Scotland 86 minutes to find the breakthrough against the Faroe Isles in Torshavn last month. It's unlikely to be as swashbuckling as his last two outings with Celtic, with the Parkhead side having hit three and four goals in successive away matches.
“Every international game is tough, every game in Europe, no matter what level the opposition are, is tough,” said Turnbull. “Teams always give 100 per cent. Usually they are decent enough at playing football as well. We know how hard it is going to be. They showed at Hampden how much of a test it is going to be. It is about combating their style and going and getting a result.
“We knew what we were going to face going over to the Faroes. They had caused other teams in the group problems. It was about sticking to our task, playing the way we can and getting the result in the end. That is what we did and we were delighted with that.”