Chelsea have attempted to sign Kai Havertz for €65 million (£58m/$76m) with another €15m (£13m/$18m) included in add-ons - but the offer remains €20m (£18m/$24m) below Bayer Leverkusen's €100m (£87m/$118m) asking price.
The Blues had waited until the completion of Leverkusen's Europa League campaign before advancing talks for the 21-year-old who remains their priority transfer target, alongside Leicester City's Ben Chilwell.
The Germany international has already spoken of his intent to leave his boyhood club this summer and he has verbally agreed on the personal terms that the west Londoners are offering.
It now looks almost certain that he will become the most expensive German football transfer of all time, after Timo Werner's £47.5m ($62m) move to Chelsea two months ago. He would also likely be the Blues' all-time record signing ahead of Kepa Arrizabalaga, who cost £71m ($93m) to bring in from Athletic Club.
Still, the Blues need to agree on a fee to complete the talks and Leverkusen's sporting director Rudi Voller has taken a strong public stance.
He explained that no discounts are available, in an interview with Gazzetta dello Sport : "No, but with his talent, it means he's on the list of all the best clubs.
"We know of the interest of a couple of clubs, especially Chelsea, but for us, the situation is quite simple; he has a two-year contract, if anyone wants him on our terms, fine, otherwise he stays here another year and we are happy. It won't be easy, but for an artist like him, there is no Covid discount."
Leverkusen CEO Fernando Carro has admitted publicly that Havertz wants to "take the next step" in his career, with only Chelsea currently negotiating to sign him.
Meanwhile, Real Madrid have to sell before they buy in this transfer market as the coronavirus pandemic hits some clubs worse than others. The Spanish giants are unlikely to be able to raise the €100m despite initially having been the versatile midfielder's first choice.
Having scored 18 goals and provided eight assists in all competitions in 2019-20, Havertz has emerged as Germany's outstanding young talent, with Frank Lampard having publicly referred to him as a "top player".
Meanwhile, Chelsea are hoping to sell Emerson Palmieri to help fund a move for Chilwell which could break the world transfer record for a full-back.
Chelsea may look at strengthening their goalkeeper and centre-back positions after poor defensive performances throughout the entirety of last season.
However, Kepa looks difficult to sell due to Chelsea's attempts to make back most of the money they paid for him, while even his salary is leading to only cautious loan approaches from Valencia and Sevilla.
Furthermore, it is expected to be a weak centre-back market this summer with many of the top players opting to stay in their current clubs.