The 23-year-old insists the reigning champions will enter the tie as favourites, and is confident that they will continue their fine form against the Gunners.
However, Smalling maintains that the Red Devils will enter the game confident of victory.
“We are going into the game with a lot of confidence,” Smalling told ManUtd.com. “We drew with Real Sociedad in the week but we had a lot of chances to win the game and I think we have gained a lot of confidence from our run of late. We are playing at Old Trafford and really looking forward to it."
United currently sit eight points adrift of leaders Arsenal and many have suggested that defeat would leave them out of the title race before the end of November.
Smalling - who signed for the club in 2010 from Fulham - refuses to accept that the game is must win, however.
“I don’t think there are any must-win games at this stage but it is still obviously a massive game."
Moyes' side are unbeaten in eight, but the record is marred with several disappointing draws - including Tuesday's bore-draw against Real Sociedad.
But despite the Champions' stuttering form, Smalling wants to take the game to the Gunners.
"We are at home and we have to be the favourites to win," he added. "We have to take the game to them and show that we are the team that wants to win and close the gap.”
In contrast to United, Arsenal are flying, with several stars in top form.
The likes of Aaron Ramsey, Mesut Ozil and Olivier Giroud have been on fire for the Gunners, but the Manchester United defender is confident they will find weaknesses in Arsene Wenger's side - and exploit them.
“We will look at the videos and see what they are doing well. As a defence, we will then work on things to minimise their impact but we won’t think about it too much. As a whole team, they are playing very well. We will find out their negatives and weaknesses, then try to punish them.”
United are in good form against the Gunners, with Arsenal winning just one of their last 11 visits to Old Trafford.
However, they will be boosted by the return of Mathieu Flamini and Jack Wilshere.