The rescheduled fixture will give United less time to prepare for Saturday's trip for Wembley. It will also disrupt their plans this week and Ward hopes Palace will benefit.
"That might play into our favour," he said today. "But we know it is going to be a tough game. We are playing against Manchester United so it is never going to be easy. We will just make sure we prepare right and have a good week leading up to the game.
"It is one of the biggest games in the club's history. We are going to fight and make sure we are ready to give a good account of ourselves. Hopefully we can do that."