The Blades did well to hold on for a draw in the initial tie after being reduced to 10 men soon after half time.
Both sides come into the game on the back of 3-0 defeats at the weekend and on runs of four games without a win in all competitions.
Rene Meulensteen was the busiest Premier League manager in the recent transfer window, making seven signings.
The winner will go on to play Nottingham Forest or Preston North End in the last 16.
Possible starting lineups
Fulham: Stockdale; Passley, Heitinga, Senderos, Riise; Duff, Tunnicliffe, Karagounis, Kasami; Rodallega, Mitroglou
Blades: Long; Brayford, Maguire, Collins, Hill; Flynn, Harris, Coady, Murphy; Porter, Paynter
Sports Mole says: 2-0