Andoni Iraola’s AFC Bournemouth travel to Old Trafford hoping to secure a repeat result to their 3-0 victory in Manchester last season.
But the Basque boss said his side must be at the top of their game to come away with anything from the match.
Asked what the key will be at Old Trafford, he told the Daily Echo: “For a lot of things, the key is there is not one key. I think we need to do a lot of things very well.
“But the key is to win the duels against very good players.
“We have to impose ourselves. You can prepare for a lot of things, but at the end, if it's one against one and you cannot deal with your opposition it’s very difficult.
“So this is the first part. From there we can maybe have chances, but if we are not good in our duels, it's going to be difficult.”
Ruben Amorim’s side have been lining up with a back three this season, but Iraola said the Portuguese coach’s team have a lot of different options from the same starting structure.
“Sometimes they go with a wing back more defensive, sometimes they go with a wingback more offensive,” Iraola explained.
“Sometimes the two holding midfielders, the more defensive player is on one side, the other they play the other side.
“From the two tens, one more is more a winger, the other one is more a midfielder.
“So from the same starting [team] in the picture you put in the same positions after when you are playing, really they have different positions and you have to adapt and they are this kind of team that they play with players in between positions.
“They adapt; you react like this, you mark me with one centre back, then I will go more open. You mark me with a full back, I will go more [closed].
“So, it's going to be a matter of defending in uncomfortable positions sometimes and don't give them all the time in the world on the ball so they can do the patterns that they want to do.”
The Cherries travel to Old Trafford on Sunday, December 22. The game kicks off at 2pm.