England boss Gareth Southgate fears Ben Chilwell and Mason Mount could be out for 10 days after having to self-isolate.
The Chelsea duo came into contact with club teammate Billy Gilmour after the 0-0 draw between Scotland and England last week.
Gilmour has since tested positive for COVID-19, forcing Mount and Chilwell to self-isolate.
"My biggest hope is for the two boys – that they're not going to miss 10 days of a European Championship," Southgate said before England beat Czech Republic to seal top place in Group D.
"That would be a massive blow for us, but for them as well. We just have to see how it plays out.
"We're not being overzealous in that we've got to follow the guidelines. If there is any risk with these two players, then we've got to make sure we don't put any other players at risk.
"The ins and outs of what would classify as being contact – they are the discussions that are ongoing.
"I was on the training pitch when I found out, so we'd just literally finished training. We'll need to go through details with the players in the morning really, so we'll have to know by late tonight or first thing in the morning of their availability and if not we'll just have to play on without them.
"We've been living on edge with that the whole season. Every round of testing you're waiting wondering if you're going to have to make a change to your team and this is the first time it's happened to us.
"As we sit here at this moment in time, that's looking a high possibility. These things can happen. We've just got to adapt and adjust."
