Manchester City manager Roberto Mancini says he didn't expect Leonardo to cross the divide and swap Milan for Inter.
Leonardo accepted Massimo Moratti's offer to coach Inter in December following the dismissal of Rafa Benitez despite his past with Milan.
Speaking to Mediaset, Mancini said: "I didn't expect Leonardo to go to Inter.
"He is doing well and the Scudetto is his property, and the derby will be decisive."
Mancini was then asked about the progress of Mario Balotelli at Eastlands.
"This year he has been very unlucky because of the injury to his knee, but he can change games by himself if he wants, so it only depends on him."
Pressed for his opinion on the whistles Balotelli got when he returned to San Siro to watch Inter last weekend, Mancini replied: "He came through the ranks with the Nerazzurri, so it's normal that there might be some angry fans.
"The fact that they continuously write that Milan want him and that there might already be an agreement doesn't bother me.
"We don't sell strong players. If anything we buy them."