The FA is exploring the possibility of Ben Chilwell and Mason Mount taking part in socially distanced training with the full England group so they can be in contention to face Germany.
The Chelsea pair are isolating after being deemed close contacts of club team-mate Billy Gilmour, who tested positive for Covid following the goalless draw between England and Scotland.
The FA is looking into precedent under Premier League project restart last summer when players worked in groups of five without contact or tackling.
Mount and Chilwell trained at a private location on site at St George's Park away from the full squad on Thursday.
Under Covid compliance rules, they must isolate up to and including Monday June 28 - the day before the last-16 game between Germany.
England wrapped up their group stage fixtures without Mount and Chilwell, beating Czech Republic 1-0 to top Group D and secured a round-of-16 game 'at home' at Wembley.
If they overcome Germany on Tuesday, England's quarter-final opponents will be either Sweden or Ukraine next Saturday in Rome.