Chelsea midfielder N'Golo Kante was allowed to miss training on Wednesday after expressing concerns over the safety of a return to action amid the coronavirus pandemic, the PA news agency understands.
Kante trained on Tuesday as Chelsea and a number of other Premier League clubs resumed non-contact sessions in the first major step towards a resumption of games.
However, he missed Wednesday's session with the full backing of the club and manager Frank Lampard.
It is unclear when the France international will train again.
Kante's decision came after six people tested positive for Covid-19 following the first round of Premier League testing this week, including Burnley assistant manager Ian Woan and Watford defender Adrian Mariappa.
Mariappa was among three Hornets staff to test positive and the 33-year-old had no idea how he caught the virus.
Mariappa told the Telegraph: "Ever since I got my positive result back on Tuesday, I've been scratching my head to try to work out how I might have got coronavirus.
"It was a big surprise because I haven't really left the house, apart from some exercise and the odd walk with the kids. I've mainly just been homeschooling and keeping fit.
"The club doctor called to tell me and, to be honest, I did ask whether it could be 100 per cent accurate or whether my results could have got muddled up. Maybe if I had been displaying any symptoms then it might have made sense. But in my head it wasn't adding up.
"I've not had any symptoms and I've felt as fit as ever, probably fitter because I've been working really hard. I've been following my training programme and I've not felt out of breath or ill, or anything.
"We've been fully monitored the whole time and the club have been able to track our distances and things.
"I've been really excelling in all of that. It's quite scary how you can feel absolutely fine and not really have left the house, and yet still get the virus.
"If it wasn't for the fact I had gone back to training and had this test, then I'd never have found out that I had the virus and I would just be getting on with things as normal. That's obviously quite a strange thought."
But the Jamaica international was disappointed the results have ended up revealing his identity.
"I'd have preferred if everything had been kept private," said Mariappa.
"But once Watford's name came out then my phone went mad with people asking who it was and I'm sure it was the same for all of the rest of the staff and players.
"For your family, you'd rather keep it to yourself, but, unfortunately, that hasn't been possible. It's disappointing that rumours started, but I will just get on with things now and follow the protocols."
Watford captain Troy Deeney has already said he would not return to training to protect the health of his family, with the club posting pictures of some of the squad back at the training ground on Wednesday.
Harry Maguire was impressed with the safety measures as Manchester United returned to training on Wednesday.
The defender told his club's website: "It seems such a safe environment. It's our first day back, but it seems so safe and everyone is respecting it so well, so long may that continue and I'm sure no one will have any problems.
"There is a lot less people at the training ground when we go in. I was in a group of four, working with one coach, so not many people. You've got a lot space, big areas, not going really close to anyone, but the main thing is getting the work in and it was a tough session.
"I think every 30 minutes we have a different slot and each slot is taken by a different coach at the club.
"It's obviously strange and something that we're not used to, but at the moment it's just getting the base fitness, the physical fitness and I think it's good mentally as well to come into the training ground and get used to the surroundings again."
