Frank Lampard believes patience is the key to seeing Kai Havertz flourish as the Chelsea playmaker wrestles with the after-effects of coronavirus and the burden of a hefty price tag.

Havertz has yet to set Stamford Bridge alight since arriving from Bayer Leverkusen for £70million during the summer despite being a fixture in the team when available.

The 21-year-old Germany international was forced to miss all but two games in November after being diagnosed with Covid-19 and it has since emerged he became very ill, cutting short the signs of promise evident before he caught the disease.

Lampard insists Havertz is still finding his feet ahead of Manchester City's visit to Stamford Bridge and has been mentoring him behind the scenes in the expectation he will eventually realise his full potential.

"Kai had five work days with us before he first played and that's just not beneficial to a player in any league, let alone when you're coming to the fastest, most physical league in the world," Lampard said.

"Just as Kai was coming to terms with that – and you saw some really good performances from him – he got Covid and he had it quite severely.

"He's definitely had a bit of a fallout from that physically. We know that and are trying to help him deal with that. The expectations around him... you have to put context into the story.

"Kai's talent is undoubted and I see that every day. Giving him the time to adapt to the Premier League and to our team is crucial.

"I have full belief in him and we need to give him that time, particularly because of the Covid situation. That's not a non-issue.

"The transfer across leagues to a game that is fast and physical week in, week out, every three days, is a big ask and it's not something that should be expected because we paid this amount for you or you're an international or your age or how many goals or assists you've made already.

"You can't take anything as a given. I thought that with Kai anyway and I'm there to help him.

"When he came I took on that challenge with him – this league is different so let's see how you adapt because your talents are going to be different, in a positive way that helps us.

"As a coach I know I can rely on my personal experience when it mirrors theirs. I know. I had to do extra work myself.

"Kai is different to me, particularly with the knockback of Covid because he hasn't had the time to do that extra work. We're doing it with him now.

"He'll be better and stronger for it in the end. He's a young player, so even more reason to give him time."

Chelsea host City knowing they have yet to register a win against one of the big six clubs – even during their 17-match unbeaten run that ended on December 8.

"That stat is overly spoken about. We were playing Leeds at the time and Leeds are not in the top six, but Leeds will be one of the toughest teams anyone will play this season," Lampard said.

"Last season we beat top-six teams and finished fourth. If you want to get to the top where Liverpool and City have been for the last four years, you have to win your fair share of games so I understand that side of it.

"But after 16 games of the season, I don't think it's very relevant. It's three points at the end of the day."