The 2-0 win took United 15 points clear of nearest rivals Manchester City, who host Chelsea at the Etihad on Sunday lunchtime.
Rafael insists no-one is getting carried away with the advantage, but maintains that every victory and clean sheet continues to boost the players' confidence.
"We're pleased to not be conceding and keeping clean sheets. We want to keep that going and continue picking up points," he added.
"The more clean sheets we keep the more it improves our confidence. That consistency really helps us. We know what happened last season and that every game is important. We just have to keep winning."
"I can't remember scoring a better goal. The one at Liverpool was different because it was a curling shot, but I can't remember a better one than this. I think it's my best."