Billy Gilmour has tested positive for Covid-19 and will miss Scotland’s Group D decider against Croatia on Tuesday.
The Chelsea midfielder was named man of the match on his full international debut as Scotland drew with England at Wembley on Friday.
However, he will now have to self-isolate for 10 days after returning a positive test result.
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A statement from Scotland said: “The Scottish FA can confirm that a member of the Scotland National Team playing squad, Billy Gilmour, has tested positive for Covid-19.
“Having liaised with Public Health England since the positive test was recorded, Billy will now self-isolate for 10 days and therefore miss tomorrow’s UEFA Euro 2020 Group D match against Croatia at Hampden.”
Scotland have taken one point from their two Euro 2020 matches and need a win against Croatia to have a chance of qualifying from Group D. Croatia are also on one point.
If Steve Clarke’s side progress as one of the four best third-placed teams then it's possible they would face the winners of Group E – currently Sweden - at Hampden Park on June 29.
Gilmour would also be unavailable for that potential match.
Roma head coach Jose Mourinho, who is working as a pundit over the tournament, said Gilmour was "the difference" for Scotland against England.
"The kid Gilmour in midfield, he made the difference," he told TalkSPORT.
"He was fantastic. He was always moving, always showing, he wanted the ball, he was turning under pressure. He linked the game much, much better."
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