Many people believe the Slovenian is the best keeper in the world. Their argument is that he is not only because of the saves he makes, but because he never makes mistakes. Therefore, what happened for Sevilla's goal was worth remembering.
There was nothing Oblak could use as an excuse like his view was obscured or he slipped or anything like that. He just simply made a mistake.
You have to see it to believe it. From a set piece, Jesus Navas sent a free-kick into the box and Franco Vazquez headed towards goal. It was a good header, but one Oblak should have saved.
However, Oblak, who threw himself well towards the ball, was unable to save it. The ball went through him and into the goal.