"Ben Foster is a good goalkeeper, there is no question about that, but the same can be said of myself and Tomasz Kuszczak.
"We are all working hard to reach the highest level we can, but people tend to be focused on Ben because they relate it to the England situation.
"I must perform and make sure I'm fit and playing at the level everyone wants me to be at."
Van der Sar could be handed his first taste of pre-season action in Saturday's Ole Gunnar Solskjaer testimonial against Espanyol.
He may also feature against former side Juventus in next Wednesday's Old Trafford friendly, before which the players will parade the Premier League and Champions League trophies around the pitch.
Tickets are still available and can be bought online or by calling 0161 868 8000.