Milan won 2-1 at the Bentegodi, but the deadlock was broken by Robinho controlling the ball with his arm to fire in.
"It was an evident handling offence. I had a clear view from the bench and saw it straight away," shrugged the Flying Donkeys Coach.
"The shame is that the referee was also perfectly placed to see it. It was a clear mistake and you can see the defenders stopped too as they appealed for the free kick.
"Admittedly, we could've been more careful to close down Robinho, but it's a shame about that handling offence."