United face Valencia on Tuesday night, and will top their group if they don't lose to the Spaniards.
If they do, United will avoid the 2009 European champions Barcelona and nine times winners Real Madrid in the first knockout stage early next year.
Keeping one out: Edwin van der Sar saves a shot from Rangers' Steven Naismith during their Champions league clash last month
'It is quite clear,' said the 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.'
United haven't had the toughest of groups, which has also included Scottish champions Rangers and Turkish outfit Bursaspor. It will still be notable however if they go through without conceding a single goal.
Rallying call: Van der Sar
Van der Sar is satisfied with the clean sheets, saying: 'So far we have not played against the biggest teams in the Champions League. Maybe that has something to do with it.
'When you start playing a higher standard of opposition it is going to become more difficult.'
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