Drogba, of Shanghai Shenhua, is being linked with Milan and Juventus.
"If both Robinho and Pato leave, we will only buy one striker because we believe the right number of strikers should be five," said Galliani.
"Is (Didier) Drogba possible? No. (Javier) Pastore? No, because we've asked Paris Saint Germain and they won't let him go."