The 24-year-old has struggled to make an impact at Anfield since his £16 million move.
The Liverpool forward was given the sanction for posting an offensive social media message.
Brendan Rodgers’s side set up a semi-final against league leaders Chelsea with an impressive performance.
Van Gaal told reporters the 24-year-old was injured in training on Saturday.
Marc Lewis says the battle between the country’s most successful clubs always provides drama.
The bitter rivals will meet again at Old Trafford on Sunday.