Clarke’s plans for the decisive Group D fixture against Croatia at Hampden on Tuesday night were rocked on Monday morning when he was informed Gilmour had returned a positive Covid-19 test.
The 20-year-old has no symptoms but must isolate for 10 days. The rest of Scotland’s 26-man squad all returned negative tests and no close contacts were identified.
Clarke is understandably keen that the bitter blow of Gilmour’s absence does not distract his players from the task in hand as they attempt to become the first Scottish team to progress beyond the group stage of a major tournament finals.
“This is a big game so let’s not lose focus on where we are and what we’ve done to get here, including the point we got at Wembley the other night,” said Clarke.
“What we have to do now is make sure that Billy’s good performance against England doesn’t go to waste.
“The players don’t need any added motivation but this is a very tight knit group. They know if we can progress far enough into the tournament, then they can welcome Billy back into the squad. That would be fantastic.
“But the first step to doing that is to make sure we go out and play as well as we can against Croatia. We have to find our top performance level and hope it’s enough to get us the three points against a team that was in the last World Cup final.
“Billy was going to start, as you would imagine after the way he played against England. So I have a change I need to mull over and think about. Hopefully I’ll come up with the right solution.
“First and foremost, I’m upset for Billy. As you’d expect, he’s very upset. But it’s just the times we are in. You have to adapt and deal with it and that’s what we’ll do.”
Like Scotland, Croatia have taken just one point from their first two games but Clarke is wary of the narrative that the 2018 World Cup finalists are a team on the wane.
“They are obviously looking for a little spark in the tournament,” he said. “But they are good players, make no mistake about it and they are going to cause us a lot of problems. We’re going to have to play our best game. We’re going to have to play as well as we can to get the result we want.
“People may say they are past their peak but they always qualify for tournaments, have top, top players in their team and we need to respect them.
“Then we have to go out there and find a way to beat them because, as much as they want to make it to the knock-out stages, so do we.
“Croatia will have enough legs in their team, don’t worry about that. They know better than us what it takes to get into the knock-out stages of a major tournament because they’ve been there before and we haven’t. They are wily old foxes but we’re ready for them.”