Chelsea are currently 15 points behind Manchester United and the Blues will need a victory in order to climb above Tottenham into fourth place.
“It’s a very important game for them, for us, for the future of Manchester United and the future of Chelsea,” said Ancelotti.
“We are excited to play this game. We arrive at it at a good moment. We have confidence to do our best and win it. It won’t be easy.
“United have been, until now, the best team in the Premier League.
“For us, it’s important to win, not just for the result but to improve our confidence after the victory at Copenhagen, where we played very well.”
Ancelotti added: “United can decide their own destiny.
“Our aim is different at this moment. Our aim is still to compete with them.
“We are not mathematically out so we have to keep believing.
“But we need also to be honest, it would be difficult for us to close the gap.
“We want to arrive in the top four – this is our aim.”