Dreesen confirmed that the huge bid for Germany international Muller had arrived when his former Bayern coach Louis van Gaal was at Old Trafford.
Bremen are third from bottom and a point above the relegation zone after losing four games in a row.
Newly-promoted Leipzig have enjoyed an outstanding debut season in the German top flight and are second in the table with 14 league matches left.
Arturo Vidal has told Sport Bild that rumours he could leave Bayern Munich for Chelsea are wide of the mark.
Fans were on two buses stopped by police on the way to Dortmund's game at Darmstadt last weekend.
Bayern Munich goalkeeper Manuel Neuer rubbished media speculation linking him with a move to join Manchester City.