The Germany centre-forward is arriving on-loan from West Ham, with the deal to be rubberstamped on January 1.
Vieri told La Gazzetta dello Sport: "Everyone was saying that Milan needed a real number 9, and they signed him immediately.
"Now he has to settle in, but in the meantime he's already solved one problem: Pulisic and Leao, also thanks to the contribution of Modric and Rabiot from the back, have put in great performances so far, but their characteristics mean they can't provide presence in the box and physicality.
"The new German arrival adds these qualities: Allegri is a master at managing him, it's up to him to know how and when to use him."
Related：
West Ham United
Milan