United have lost against all three teams away from home this season. On Saturday United lost 2-1 against Arsenal at the Emirates.
“It was a chance to get a psychological blow over one of our rivals,” said van der Sar.
“If we had beaten them, or even drawn, we would have kept them below us. Now we have let them back in.”
“We have played all three away now,” added van der Sar. “I am not concerned about our results against the top teams because we have been unlucky in all three games.
“But we have to make sure we get the nine points from the home games against them at Old Trafford.”