Gattuso says his players lacked "hunger" for the shock loss.
“We should not have lost a game like this. Possession is fine, but not when it's sterile, as we tickled the opposition rather than hurt them," Gattuso told Sky Sport Italia.
“There were some good things in the first half, but after the break we were making too many predictable passes to feet, never a give and go.
“We need more vehemence and hunger, as today we didn't do enough off the ball."