Frank Lampard has backed Kai Havertz to realise his "top-class" potential at Chelsea now he is putting his coronavirus illness behind him.

Havertz missed several weeks of the campaign after testing positive for Covid-19, with Lampard now revealing the condition took a greater toll on the Germany playmaker than previously thought.

The 21-year-old has yet to find top form over a sustained spell since joining the Blues in a £70million summer switch from Bayer Leverkusen, but Lampard has tipped Havertz to become of the world's best players in his time at Stamford Bridge.

"Kai is fitting in really well, I said it before but I want to make it clear that he had strong symptoms of Covid," Lampard said ahead of Tuesday's Champions League clash with Krasnodar.

"He was very ill and struggling for a while and not all players have it like that, some are symptom-free.

"I had to factor that in so that's why it took two or three weeks before he is starting a game again after he returned from Covid.

"Before he fell ill and turned in a positive test, I thought his form was fantastic.

"He played some really good stuff in the number eight role, the advanced midfield role and I was delighted for him. You could see he was enjoying it, but Covid cut that short.

"Long term, I have no concerns. In fact, I feel quite the opposite. He is going to be a huge player for this football club, in the Premier League, as he has all the attributes and attitude to be an absolutely top-class player for the league and in the world.

"That's how highly I rate him and I think people that analyse him, it can be quick reactions at times involving price tags and so on.

"But I think we have to understand that some of the best players that have come to this country have found it quite hard for some time to get used to the Premier League and I think Kai has actually been very good.

"Covid has made it difficult for him but he is a top player and will be a top player for us."