The Dutch legend, who joined Sir Alex Ferguson’s side in 2005 and went on to feature in more than 250 matches, retired following United’s recent Champions League final defeat to Barcelona at Wembley, in which Pep Guardiola's side ran out 3-1 winners.
However, Van der Sar believes that if Ferguson continues to steer the club in the right direction, having recently secured the club a record 19th Premier League title and added to the squad with the signing of highly-rated defender Phil Jones, then it is only a matter of time before the tide turns.
"Of course they will improve and grow next year - and that's what they have to do," Van der Sar said.
"At the minute Barcelona are better than us and that happens - sometimes in your life you come up against people who are better than you; it's what sport is about. So you have to learn to compete against them.
"At this moment we aren't good enough and that hurts, but there's no reason why the team cannot come back next year and the year after.
Meanwhile, Van der Sar has hinted that his six-year stint with the Red Devils has meant he will stay a life-long supporter of the club and is certain that Ferguson has the commitment and focus to ensure his side can one day match the Catalan giants.
"I won't be there but I will be watching! I know the manager will build a team that is capable of challenging Barcelona; it will be a big incentive for him."
