Manchester United boss Louis van Gaal has given his players Friday off.
United face Arsenal in London on Sunday.
"The solution is recovery, recovery, recovery," he said at his pre-match press conference. "That is why it's so difficult to prepare for the match against Arsenal.
"As a manager, you want to prepare on the pitch and you cannot do it because you need freshness of the players, so then there's also another solution - to change your squad.
"So we have to see how the evaluation is from my fatigue specialist. I cannot tell that because the press conference is one day after the match.
"Tomorrow, they have a day off because they've already had two weeks with no day off.
"We have to wait and see for Saturday and then I can make decisions."