Billy Gilmour's World Cup dream has come to a devastating end after the Scotland midfielder sustained a knee injury during his country's 4-1 triumph over Curacao at Hampden.
The Napoli player, 24, went down without any contact in the opening half and had to be withdrawn from the match immediately.
Post-match scans confirmed damage to his knee, forcing the midfielder to head back to Italy where he will undergo rehabilitation with his Serie A club.
The blow comes at the worst possible moment for Scotland, who are set to face Haiti in Boston for their opening World Cup fixture in just over a fortnight.
Billy Gilmour has been ruled out of the World Cup after an injury
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Steve Clarke was left heartbroken by the loss of his key midfielder, describing the situation as exceptionally harsh given its timing.
"I am devastated for Billy because he has been an integral part of our World Cup qualifying campaign. The timing of this injury is so, so cruel and we all feel for him," the Scotland manager said.
Clarke emphasised the high regard in which Gilmour is held within the squad, both professionally and personally.
"He knows what we all think of him as a footballer and a person and while no words will give him any comfort tonight, I am certain Billy will have many major tournaments ahead of him in the future," he added.
The man who came on for Gilmour made an immediate impact, with Findlay Curtis netting his maiden senior international goal to draw Scotland level after Tahith Chong had given Dick Advocaat's side an early advantage.
Steve Clarke has revealed he is "heartbroken" for Billy Gilmour after his World Cup-ending injury
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Lawrence Shankland then struck twice, with Ryan Christie converting from the penalty spot to complete the scoring before the squad departs for the United States.
Clarke acknowledged that Jurgen Locadia's dismissal seven minutes before half-time fundamentally altered the contest.
"The red card obviously changes the whole dynamic of the game and from there, at least, against the 10 we managed to start creating chances and got a few goals," he said, adding that an 11-versus-11 encounter would have provided a sterner test.