England players Mason Mount and Ben Chilwell have been forced to self-isolate after coming into close contact with Billy Gilmour – the Scotland midfielder who tested positive for coronavirus.
Gilmour was named man of the match in Scotland's 0-0 Euro 2020 Group D draw at Wembley on Friday but it was confirmed on Monday he would have to isolate for 10 days, forcing him out of Tuesday's crunch clash with Croatia at Hampden Park.
England also conclude their group campaign with a match against the Czech Republic at Wembley, although manager Gareth Southgate has now had his plans disrupted after Mount and Chilwell interacted with their Chelsea team-mate.
"We don't know at the moment," Southgate said when asked at a pre-match news conference whether the pair would be available to play.
"There's got to be quite a doubt but there's still a lot of discussions and investigations going on behind the scenes,
"At the moment they are isolating, we just have to find out over the next 12 hours or so."
The duo returned negative lateral flow tests on Monday and trained with their international colleagues but, on the advice of Public Health England, they will now be kept away from the rest of Southgate's squad and backroom staff until further advice is received.
"As a precaution at this time and in consultation with Public Health England, Ben Chilwell and Mason Mount are isolating after interaction with Scotland player Billy Gilmour at Friday's match," a statement published on England's official Twitter account read.
"The pair will be kept away from the rest of the England players and wider support team, pending further discussions with Public Health England.
"The entire squad had lateral flow tests on Monday afternoon and all were again negative, as was the case with Sunday's UEFA pre-match PCR tests.
"We will continue to follow all COVID-19 protocols and the UEFA testing regime, while remaining in close contact with Public Health England."
In the event of a 10-day isolation period, beginning from their contact with Gilmour, Mount and Chilwell would be ruled out of facing the Czech Republic – who are level on four points with England at the top of the group – but would be available to return for a potential last-16 encounter on Monday or Tuesday of next week, providing they do not return a positive COVID-19 test in the interim period.
Left-back Chilwell is yet to feature for England at Euro 2020 and did not make the matchday squad for their opening 1-0 win over Croatia.
Mount, who had been due to take part in the news conference alongside his boss, has been an integral part of Southgate's side for some time, however, starting both Three Lions' matches at the tournament so far.
England's performance in the draw with Scotland was heavily criticised and if Mount has to sit out against the Czechs, it would only further increase the clamour for Aston Villa's Jack Grealish to be handed a starting berth.