Hayes said players have become concerned about having another Christmas affected by an outbreak.

"Our heads were all over the place, we are human beings," Hayes said.

"A few days ago we had two players stuck down with Covid, we know inevitably that when we land tomorrow there will be positive cases [when players are again tested].

"When you are in a team environment, you know it spreads like wildfire in the team. I'm gutted for the players because we know that was nowhere near a team that represents my team."

Hayes said she "takes responsibility" for the defeat by Wolfsburg, when a point would have seen her side win the group and advance, but she added that the the situation "has been really difficult to manage".

Last year her squad, which includes a number of international stars such as Australia's Sam Kerr, Dane Pernille Harder, Norway's Guro Reiten and South Korean Ji So-yun, were unable to leave England to spend time with family because of the pandemic. Hayes said there were 20 cases of Covid at Chelsea 12 months ago.

An outbreak at the club threatens to again keep the players in London for the festive break.

"I have players being sick in there, they have got diarrhoea, they are exhausted and maybe some of that mental anxiety plays a part in it," said Hayes, whose side were beaten by Barcelona in the Champions League final last season.

"I just feel that this was deja vu and we are here 12 months after a really bad Covid outbreak at the same time."

Hayes joined the growing number of voices in English football calling for a postponement of fixtures because of Covid-19.

"We do not get paid millions of pounds, I want my players to go and see their families," she said.

"It's across the game at the moment. For me it's a major reason behind performance tonight.

"You are a player and you don't want to go to the dining room, don't want sit with team-mates and you don't want to go in the dressing room. It's a team sport, you have got to be together but you don't want be together because you don't want to get it off anyone and you don't want to pass it on to anyone.

"It's quiet, its sombre. It feels like you are sitting in a waiting room for something to happen. That is really difficult to switch from to go and perform."

The Chelsea boss added that she "didn't recognise her players" because of the "pressure on some of their heads".

"Unfortunately we could separate that anxiety from the performance," she said.

"I can honestly tell you that I didn't recognise my team tonight, I've never seen a performance like that from them."