New boss Jose Mourinho won his first three league games in charge, however a dip in both results and performances means the current FA Cup holders go into the game two places and six points behind the Gunners.
Petr Cech knows the Portuguese manager very well, having been managed by him in two different spells during his eleven-year spell at Chelsea, and he believes that Arsenal can end United's hopes of winning this year's Premier League - even though it's only November.
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Cech on Man United vs Arsenal
When speaking about the highly-anticipated encounter, the 34-year-old goalkeeper told Arsenal Player, via Goal: "It is another six-point game. We drew the match against Spurs and there is a little gap between us and Liverpool.
"So you want to make sure that you stay very close and that every time they (Liverpool) drop points, you are ready to take advantage."
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On Man Utd's title ambitions, the Czech continued: "With United, they are behind us, so to leave them (further) behind is one aim and the second thing is to stay near the top, within touching distance of everyone else.
"If United want to think about closing the gap and having a chance to fight for the title, they need the three points. It is a big game for both teams and they will try to give themselves a chance, and we have to be ready to adapt to their way of playing.
"As (far as) the match goes, you want to impose your game and control what is happening. It is always a big game, regardless of the positions of both teams in the table, but this time I think it could be a really significant win for us and a really significant loss for them."
As things currently stand, a victory for Arsene Wenger's side would keep them extremely close to Manchester City, Chelsea and league leaders Liverpool, whilst leaving United nine points behind them.
However, a home win on Saturday will see the Red Devils move level on points with fifth-placed Tottenham (having played a game more) and just three behind Arsenal, who are currently in the fourth and final Champions League place.
Who do YOU think will win Saturday's clash? Man Utd or Arsenal? Or will it be a draw? Leave YOUR opinion in the comments box below!