The leaders stretched the advantage at the Barclays Premier League summit to four points on Saturday evening, having at one stage given hope to Chelsea and Manchester City that they could end the weekend in first place.
The trademark comeback at Aston Villa, turning a two-goal deficit into a wonderful 3-2 triumph, instead left Roberto Di Matteo and Roberto Mancini's sides needing victories against Liverpool and Tottenham respectively just to close the gap.
"I think it's a massive win," Smalling told MUTV. "Especially with the other teams looking at that result when they have got big games on Sunday. It puts pressure on them."
Smalling was given a physical examination by Villa's summer signing Christian Benteke in a second game of the week after missing the start of the season due to injury.
"I'm feeling good actually," he revealed. "I've been thrust back into action but that's what I wanted. Hopefully I can stay fit and carry on. They had a strong striker up front so we had a good battle but, luckily, we won in the end. I think, to be fair, I got sucked in by him for the first goal but we just had to come out for the second half and put on a performance. Thankfully, Chicharito came up with the goals."
Sir Alex Ferguson accepted that the former Fulham man was given a rough ride by Benteke, who set up the opening goal with some positive, muscular approach work down the left flank.
"Chris was in the wars a few times," stated the boss. "He got a lot of knocks. He was up against a real handful today, Christian Benteke. He did