Dortmund's star striker Robert Lewandowski has been strongly linked with a move to Bayern Munich, which has led to reports that Diouf has been lined up as his replacement.
Slomka, however, has said that the Senegalese is a big part of his plans at Hannover.
"We are planning with Mame Diouf, and want to extend to his contract," Bild quotes Slomka as saying. "He's not for sale."
Diouf has scored 14 goals in 26 league games for the Bundesliga side.