LONDON (REUTERS) - Chelsea midfielder Kai Havertz has said that contracting Covid-19 opened his eyes to the debilitating effect the virus can have on people and left him with such severe fatigue that he felt like he had not played soccer before.

Germany international Havertz, who joined Chelsea from Bayer Leverkusen during the close season for a reported £71 million pounds (S$125 million), tested positive for the novel coronavirus in November and missed three matches.

The 21-year-old has since recovered and started the London side's last three games in all competitions but said beating the virus was a tough challenge even for a youngster like him.

"It was like a very bad flu for me, so now I know it is very bad for people. Before I sometimes thought, 'OK it's not so bad'. But now I get it, and I know for older people and people who had illnesses before it can be bad," Havertz told the BBC.

"We all have to look out for each other. It was personally hard. When you do nothing for two and a half weeks and then you start training again, you feel like you've never played football before. For me it took two to three weeks to get back to 100 per cent.

"Now I've started three games and I'm feeling good. It takes a lot of time, it took around one and a half months for me to get back, but now I think I'm fit again and can start to attack again."

Havertz has started eight games in the Premier League this season, scoring once.

He netted a hat-trick in his lone League Cup match against Barnsley in September.

Chelsea, who are third in the league with 22 points from 11 games, visit Everton on Saturday.