The Eagles are away at Old Trafford in the final eight of the competition but manager Freedman also has to be wary of the Friday night league clash with Derby County at Selhurst Park.
"We've got to take into account that 48 hours later we are playing Derby live on the television, so we've got to make sure we are also prepared for the quick turnaround," said Freedman.
"I will be very shocked if 20 players don't get some game-time over the next two matches. I will be mixing both teams around to give me the best opportunity to win both games.
"There will be an opportunity for some players who haven't played so many games to play in one of these games. I will be picking a team that I believe can hold on for as long as possible against Manchester United and then pick a team that can hopefully beat Derby."