The Chelsea legend insists new signing Nicolas Anelka cannot hope to replace Drogba and told The Sun: "Anelka has huge potential but Drogba is Drogba.
"He will be there competing with Andriy Shevchenko and the other strikers but you cannot replace Drogba because he is the best.
"I don't know if Anelka can be the real first choice for Chelsea all the time."
The World Cup winner added: "It will be hard for them to play together.
"Anelka doesn't really like to stay up front and he moves around a lot.
"Drogba goes right and left and it will need a lot of work for them to form a partnership."