You just have to feel sorry for Daniele Padelli in this case. Under no pressure from the striker, Padelli scuffs his clearance. Somehow, he mishits the ball so much that he puts that exact right amount of spin on the ball to put it in the net.
If goalkeeper howlers is your kind of thing, here is a pick of recent goalkeeping errors for your enjoyment. Padelli’s mistake definitely deserves to be in this video.