United entertain Valencia at Old Trafford on Tuesday night with their place in the last 16 already confirmed.
And, while United tend not to express concern about beating anyone, Van der Sar feels their chances of progress would be better served by taking a route to Wembley next May that avoids the Spanish giants.
"It is quite clear," said the veteran Dutchman.
"We are through now but we want to get top spot in order to avoid any of the bigger teams in the earlier rounds.
"That is what we need to do against Valencia."