Chelsea will have to pay Jan Oblak's €120 million (£110m/$137.5m) release clause to force contract talks with the Atletico Madrid goalkeeper.
It remains unclear whether the 27-year-old would be ready to leave Atletico this summer, with manager Diego Simeone ready to block the exit of the Slovenia international in most circumstances.
However, the relationship between Chelsea and Atleti is good, having seen the transfers of Diego Costa, Alvaro Morata and Thibaut Courtois conducted between clubs in recent seasons.
Blues boss Frank Lampard remains unconvinced with his goalkeeper Kepa Arrizabalaga, and he would need to find him an escape route to try to balance the books before considering such an offer for a player such as Oblak.
Valencia have recently enquired about possible arrangements to sign Kepa on loan, as they look to move on their current No.1, Jasper Cillessen.
Los Che would be interested in a two-year loan with an option to buy the Spain international, which might end up being Chelsea's best option for moving on the the £71m (€80m/$90m) signing from Athletic Club in 2018.
Along with the high fee, Kepa also commands high wages and currently earns £170,000-a-week, which remains a stumbling block and put off Sevilla, who are also considering signing a new goalkeeper.
The Blues have shown few problems making big signings so far in the transfer market, having brought in both RB Leipzig striker Timo Werner and Ajax winger Hakim Ziyech already.
However, they must offload a host of talent before making more big moves as they face a bloated wage bill and potentially unhappy players in the squad.
The Spanish transfer market looks set to contract more than the English one with swap deals, loans and free transfers being prioritised at even the bigger clubs. Barcelona, for example, have already had to conduct contrived deals with Juventus over the transfers of Arthur Melo and Miralem Pjanic.
Atleti were seeking to do a deal for €5m plus Santiago Arias, but this has not excited the Dutch champions who believe they could get a better deal from the west Londoners, making them favourites to meet their €26 million (£24m/$30m) valuation.
Bayer Leverkusen midfielder Kai Havertz remains a key target for the Stamford Bridge club, although details of a concrete offer have yet to emerge.