"We must make up the ground we lost in Bergamo as soon as possible," the former Udinese Coach told the Corriere dello Sport.
"I want to see my side take the game seriously and it won't be easy against Siena.
"I think the Robur have played some of the best football in the League and Marco Giampaolo is a great tactician.
"We are a stronger side than Siena, but we have to go out and prove that. There is no room for error now.
"After the Atalanta game I didn't say anything to the players. I expected a physical lapse and a loss of intensity after the friendly between Italy and Brazil."