Toni spent last season on-loan at Roma.
"You cannot contest Toni's talent, while Fred played in the Champions League with Lyon and is now in Brazil," Bigon told Radio Marte.
"We are following many options, including overseas, and keeping a close eye on alternatives. Before buying anyone, we will sell.
"Vagner Love has different characteristics to Toni and Fred, so it would change our style of football. The type of player we're looking for is a pure hitman."