LONDON (REUTERS) - Chelsea forward Kai Havertz has returned a negative Covid-19 result and is back in training a day after four teammates tested positive, manager Thomas Tuchel said on Friday (Dec 17) as he branded the current situation a lottery.

Chelsea announced before Thursday's 1-1 draw with Everton that Romelu Lukaku, Timo Werner, Callum Hudson-Odoi and the injured Ben Chilwell had tested positive for Covid-19 while Havertz missed the game because he was unwell.

"No more positive tests but the lottery starts again tomorrow morning or tomorrow afternoon," Tuchel told reporters ahead of Sunday's trip to Wolverhampton Wanderers.

"We are happy at the moment that Kai has more than only one negative result so he was back in training... We left Kai out because he felt unwell and we thought there was a possibility he might be positive.

"Mateo Kovacic is back in his first training session today.

"Jorginho is a doubt as he is in pain, Ruben Loftus-Cheek is a doubt because he is in pain. I don't know if they can play on Sunday."

The game is one of five matches that were not postponed by the Premier League amid coronavirus outbreaks at several clubs.

Arsenal manager Mikel Arteta had called for the Premier League to offer more clarity on the games being postponed as it was essential to maintain fairness and Tuchel echoed those sentiments.

"It is not in my hands, but clarity and transparency is always good in every subject," Tuchel said.

"I know the rules now, I did not get involved too early. I read them and then immediately forgot them because there are so many of them."

Playing more games over the Christmas period is a first for Tuchel, who was used to a winter break during his time in the German Bundesliga and French Ligue 1.

"Normally I had a short break and holiday but then I switched on the TV and was happy to see football. It is very unique," he said.

"It is very tiring, it makes you fatigued and it's not always the most pleasant thing but at the same time it is."