Bayern Munich manager Louis van Gaal has praised Edwin van der Sar for setting a good example to young players but described the goalkeeper as 'manufactured'.
Van Gaal worked with Van der Sar during his time in charge of Ajax during the 1990s and admits he did not regard his fellow Dutchman to be the most naturally gifted performer.
However, Van der sar has gone on to enjoy a magnificent career and is now recognised as one of the most reliable shot-stoppers in the business.
He has also enjoyed great longevity as he remains Manchester United's No.1 despite the fact that he will turn 40 later this year.
Van Gaal believes Van der Sar deserves enormous credit for working so hard at his game as the pair prepare to go head-to-head in the first leg of a UEFA Champions League quarter-final on Tuesday night.
"I always say Van der Sar is a manufactured goalkeeper," said Van Gaal.
"He is not so happy when I say it, but there are more natural goalkeepers in the world.
"Van der Sar has been made into a goalkeeper. It is my philosophy to train the brain and that is the reason why Van der Sar has been around so long.
"He always works with his brain. That is his secret. He is a great role model for goalkeepers around the world."