Chelsea will have to pay Jan Oblak's €120 million (£110m/$137.5m) release clause to force contract talks, with Atletico Madrid keen to hold onto their prized asset.
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 superstar option.