Either Clarence Acuna or Nobby Solano will make way for Dyer if he makes it, while O’Brien will be replaced by Steve Caldwell or Nikos Dabizas with Titus Bramble returning on the bench.
With Alan Shearer suspended Shola Ameobi looks likely to start alongside Craig Bellamy up front.
Gary Speed, Hugo Viana, and Jamie McClen are out injured.
West Ham have Tomas Repka suspended, but Glenn Roeder does have both Lee Bowyer and Don Hutchinson available for selection.
The likelihood is that Bowyer will make his Hammers debut as a substitute.
Us: Given, Harper, Griffin, Bernard, Elliott, Hughes, O'Brien, Dabizas, S Caldwell, Bramble, Solano, Robert, Dyer, Jenas, Acuna, Kerr, Bellamy, Ameobi, LuaLua, Cort.
West Ham: James, Winterburn, Dailly, Pearce, Schemmel, Breen, Bowyer, Carrick, Sinclair, Cole, Defoe, Minto, Lomas, Moncur, Hutchison, Cisse, Camara, Ferdinand, Sofiane, Bywater.
Referee: Jeff Winter