Speaking to Manchester United Radio, van der Sar said: "It's important to keep clean sheets when we're not scoring many goals. The last few games have gone well and everyone's defending well and working hard. It shows you're a strong team and don't rely on individuals.
"We have maximum results from the last five games, even though we played better and created loads more chances in the first three. That's a bit strange but that's football."
He added: "My form's been steady this season and hopefully I can maintain it and prolong it as soon as possible. Normally I don't have too many downs in a season so hopefully I can keep it like this."