The reigning champions go into the game eight points behind the Gunners having already lost three times in the Premier League this season.
Arsenal, meanwhile, are in fine form and full of confidence following impressive victories against Liverpool and Borussia Dortmund.
While Giggs recognises Arsene Wenger’s men are in a strong position, he insists that does not make them favourites ahead of Sunday’s clash.
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“I wouldn’t say we were underdogs. But I take the point that Arsenal are probably the form team and it is going to be a tough game.
“You know what you’re going to get, they’re going to keep the ball, they have got plenty of quality and they are in good form.
“I think this season they have added a bit of steel, they’re not giving many goals away.
“Arsenal have always had the class to produce good performances and, this season, they have done it consistently. Confidence is high in their camp, but equally, we are finding a bit of form.”
After an inconsistent start, David Moyes’ men are unbeaten in their last eight games and Giggs says the team are starting to put a consistent run together.
“When Arsenal come to Old Trafford, it is always a big game,” he added. “But yes, over the years, there has been us and them going for the title and there have been some juicy meetings.
“With the start that they have had this season, they are top of the league so everyone is looking at this game as an important one.
“They had a great win in the week against Borussia Dortmund, so we are going to be up against it. But at Old Trafford we are always confident that, no matter who we are playing, we can beat them.”