Bayer Leverkusen chief Rudi Voeller has told Chelsea that they will not sell Kai Havertz unless their asking price is met.
The Germany international is at the centre of Chelsea's transfer interest this summer.
After going the year without transfers, the Blues finished fourth in the Premier League and are keen on splashing the cash now they have the chance after a ban.
Havertz is the ideal signing for Lampard, but Leverkusen have slapped a €80m asking price on the playmaker.
Chelsea chief Marina Granovskaia has been worked hard to lower that total but Bayer have told her this is the lowest they will go.
Voeller said: “Havertz? We know that Chelsea are strongly interested in him.
"But we’ll not sell any player before the end of the Europa League.
"If Chelsea want to sign Kai, they must pay what we ask. No lower price because of Covid-19."
It backs up his earlier comments made last month that he has no intention of breaking up the Leverkusen squad before the season has ended.
"Maybe I'm too old-fashioned or romantic but for me it is a matter of course that a player ends the season no matter when it ends," he added.
"There is no discussion at all for me to consider.
"Could I possibly hurt myself? Or take a little vacation?
"Then some should have withdrawn two months ago.
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"Whether it's the Europa League or the Champions League, if it's wanted by the player, the host and the club, I couldn't understand if a player didn't want to [play]."
Leverkusen overcame Rangers in the Europa League to set up a quarter-final tie with Inter Milan.
Both clubs have their sights set on winning the competition, but Bayer need to in order to land Champions League football next season having missed out in the Bundesliga.