"Diamanti literally begged us in tears to let him join West Ham," director of sport Nelso Ricci told the Corriere dello Sport.
"He said this is the opportunity of a lifetime. He thanked the President for having signed him from Prato in Serie C2, but now he wants to leave.
"West Ham will pay £5.5m in three years. What could [President Aldo] Spinelli do other than sell a player who no longer wants to be here?
"We cannot keep unhappy players. Spinelli had already improved Diamanti's contract to match the higher earners, like [Cristiano] Lucarelli."