The Dutch striker last netted in United’s 2-0 win over Everton on February 10, with his goal drought coinciding with exits from both the Champions League and the FA Cup.
But Van der Sar has dismissed criticism of his countryman, and believes he is still contributing a lot to the team despite his barren run in front of goal.
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"As a striker, all you want to do is score. But he has done his bit during the first and middle portions of the season.
"And he is still one of the best players in the Premier League."
Though United suffered defeat against rivals City on Monday, they remain on course to secure a 20th championship crowd, and Van der Sar has backed Sir Alex Ferguson’s team to finish the job.
“If Manchester United had won on Monday that would have been it,” the former Dutch shot-stopper added.
“That result would have hurt, as it always does when United lose a game. But the only way to get over it is to focus on the next one.
“The title is almost over and that is the prize they really want.”