Dunn had to be replaced after only half an hour of Rovers' match with Stoke at Ewood Park on Saturday having sustained a calf strain.
Keith Andrews also has a calf problem and is doubtful for the tie, while Franco Di Santo is ineligible.
Manager Sam Allardyce will once again be absent from the dugout as he continues his recovery from heart surgery, so assistant boss Neil McDonald will be in charge of first-team affairs for the fourth successive match.
Rovers (from): Robinson, Olsson, Chimbonda, Givet, Salgado, Samba, Nelsen, Diouf, Pedersen, Grella, Jacobsen, Nzonzi, Emerton, Hoilett, Kalinic, McCarthy, Roberts, Brown.
