Van Gaal has openly questioned the fitness of the England international, who moved to Old Trafford from Southampton for a fee in the region of £30m during the summer.
The deal for Shaw is believed to have been completed before Van Gaal became United boss, and the left-back has fallen down the pecking order following the signing of Marcos Rojo.
When asked if he felt that Van Gaal does not rate Shaw, Meulensteen told talkSPORT: "Yes. It's a big surprise for me.
"He would have been informed by the club that they were putting this bid in for Shaw because he's an up and coming player.
"He's got a good left foot and a lot of pace. He's got a lot to learn to get to a Man United level though. He's a great prospect but he's brought Rojo in, which is bad news for Shaw."
Shaw has not featured for United so far this season.