United made it successive away wins in the Premier League courtesy of a 3-1 victory against the Gunners, who found it difficult to deal with the away side's counter-attacking threat.
Romelu Lukaku was joined by Anthony Martial in the final third as Jesse Lingard operated in the number 10 role, and Smalling has paid tribute to the tactics which outsmarted Arsenal on their own patch.
Smalling told MUTV: "I think we were carrying on from Watford and the fact that, when we play, obviously in this system, we can play with two strikers. Quite often, they are only used to playing against one. We put two up front and put them under more pressure and they are not used to that.
"I think that was one to enjoy, for fans watching the game and for us as players. It was end to end, but for us to get those two early goals, I think, meant Arsenal had to come at us and that's what made it a very entertaining game.
"They probably had about four strikers on the pitch so it was a case of digging in and making sure, even the attacking players, were doing their job and everyone to a man was brilliant.
"I think Watford were going into our game on Tuesday on a great run of form and Arsenal, I don't think they've lost at home like we haven't, so I don't think we could have asked for anything more. It's been a great week."
Next up for United is a Champions League clash against CSKA Moscow on Tuesday night, where a point would be enough to book their spot in the knockout stage of the competition.