He brought on the big Belgian as he tried to salvage a draw at West Ham on Sunday, leading Sam Allardyce to refer to his side as “long ball United”.
Fellaini has not started a Premier League game since December 14, when he was part of a side that won six consecutive league matches.
“We need the guts to play football along the floor. That we have done in the second half,” said Van Gaal after the change of tactics brought a 1-1 draw.
“With him (Fellaini) we have more power. With Adnan (Januzaj) and (Angel) Di Maria, we have more creative players. The second ball you cannot always win with these players.
“But you have to win (the ball), otherwise I have to line up always (with) players like Fellaini.”
Against West Ham, the disappointing Di Maria created just one chance while Fellaini’s presence in the area led directly to United’s equaliser.