Having failed to impress van Gaal, Chicharito was sold to Bayer Leverkusen during the summer.
The decision has backfired for van Gaal as Hernandez has managed a fantastic 19 goals in just 21 appearances so far this season, while his United side are struggling to find the back of the net.
Former United defender Ferdinand has not been left impressed by van Gaal's decision to offload Hernandez and has stated that the Dutchman made a huge error in allowing the Mexican star to leave.
Ferdinand told The Sun: "Van Gaal seems to struggle to get the best out of forwards with his strict and rigid tactics. Robin van Persie suffered under him at United as did Angel Di Maria, Adnan Januzaj and Javier Hernandez.
"I loved Chicharito when I played with him. He guaranteed you goals, even when he was rotated between being a starter and a substitute. But Van Gaal didn't seem to know how to get the best out of him or wasn't prepared to adapt to the little man's way of playing.
"Yet see what happens when Chicharito is free to do it his way, he is now banging goals in for fun at Bayer Leverkusen."