Billy Gilmour has tested positive for Covid-19 and will miss Scotland's Euro 2020 match with Croatia on Tuesday.
Chelsea's Gilmour was a standout as Steve Clarke's side drew 0-0 with England on Friday - the midfielder's first Scotland start.
The BBC has asked the Scottish FA if any close contacts of Gilmour will also miss the match due to the need to self-isolate.
Scotland must beat Croatia at Hampden to progress from Group D.
Both sides have a point after two matches while England and the Czech Republic are on four points ahead of their meeting at Wembley.
"The Scottish FA can confirm that a member of the Scotland national team playing squad, Billy Gilmour, has tested positive for Covid-19," the SFA said.
"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 squad member John Fleck tested positive for coronavirus before the tournament and missed the 2-2 friendly draw with the Netherlands, along with six close contacts.
Those six close contacts returned in time for the 1-0 friendly win over Luxembourg and Fleck was available for Scotland's 2-0 defeat by the Czechs and the draw with England.