Gareth Southgate faces a nervous wait over the weekend to see how many of his England players will have to withdraw from the squad because of coronavirus quarantine rules.
Patient confidentiality means no Premier League clubs, nor the FA, have confirmed whether any England player has tested positive for the virus, but Sky Sports News has learned that a number of Chelsea players - including Tammy Abraham and Mason Mount - have been self-isolating as a precaution.
Tottenham's Harry Kane is another who has been self-isolating following his return from a holiday in the Bahamas, also as a precautionary measure.
On Thursday, the FA's medical team were confident that all 23 members of Southgate's squad would be clear of quarantine rules and free to join up on Monday morning as planned, although Manchester United striker Marcus Rashford is also a doubt, but due to an ankle injury rather than coronavirus.
Now the players' availability is less clear, and it seems inevitable some of them will be unable to join up at the start of the training camp. At this stage, it is not clear whether any player will be allowed to join up late, because of the need to keep a secure, sterile environment around the squad as a whole.
FA officials are in daily contact with the players and their clubs, and every player that Southgate has named has now had a coronavirus test.
But, under UEFA rules, each player must have a second test - and test negative - before they are allowed to join up with the rest of the squad in a bio-secure bubble at St George's Park.
Those second tests will be carried out as the players arrive in the Midlands on Monday morning.
The FA has been dealing with a much more complicated scenario than the Premier League clubs faced, when the season resumed in June.
Back then, the clubs' training grounds were secured, and players and support staff were tested twice a week.
But in the weeks since the end of the season, most Premier League players have been abroad, knowing it may be their only chance of a holiday for the next eight months.
Most have not returned to the secure routine at their clubs, and their first step back into team training will be with England.
That has led to a logistical nightmare for Southgate and his officials, as they try to track where players have been, what risk they have been exposed to, and what the individual rules are for UK citizens returning from various foreign countries.