Mauro Icardi had levelled things for Inter in the 52nd minute, cancelling out Douglas Costa's strike in the first half, and were gifted the lead 13 minutes later.
After avoiding a challenge from Juan Cuadrado, Ivan Perisic fired in a ball into the box from the left-hand side.
It squeezed through a few bodies in the box before taking an important deflection off Barzagli and flying into the back of the net, giving ten-men Inter a 2-1 advantage.
Check out the own goal for yourself:
28 April 2018