Though they first eyed Allison, Chelsea quickly turned their attention to Oblak, who is widely regarded as one of the best goalkeepers in the world.
During that summer, Oblak had an £87m release clause in his contract, with Diego Simeone refusing to accept anything less than that price.
Chelsea though were unwilling to splash that much on a keeper and decided to instead seek an alternative.
That alternative was Kepa, who himself had a sizeable release clause in his contract at Athletic Bilbao of £71m.
But the Blues decided that that fee was one they would be willing to pay and so Kepa, not Oblak, arrived at Stamford Bridge.