The front pair have both impressed since signing for the Tigers during the January transfer window, but Bruce will be unable to select them for the Wembley encounter with the Blades.
The Yorkshire club have secured several scalps on the way to the last four, overcoming Aston Villa, Fulham, Nottingham Forest and Charlton Athletic to move one game away from an unlikely appearance in the final.
Clough is expected to have a fully-fit squad to choose from for the match with the Premier League side.
Hull City: WLWLLW
Sheffield United: LWLDDW
Possible starting lineups
Hull City: Harper; Rosenior, Figueroa, Chester, Davies; Livermore, Elmohamady, Meyler, Huddlestone; Boyd, Sagbo
Sheffield United: Long; Freeman, Hill, Maguire, Kennedy; McGinn, Davies, Dimaio, Harris; Paynter, Baxter
Sports Mole says: 3-1