Ten Hag spent three years at PSV as an assistant coach.
"We had some trainees in the squad who were nice, but they did not have the talent of the top players. They were in the A1 and B1. First we pulled Zakaria Labyad from there and then Memphis. He was dripping with class. Everyone could see," Ten Hag told Voetbal International.
"While he was actually still a young player, he was already training with the big boys. Memphis was very confident of himself.
"His strength was the speed with which he did things. Memphis wanted it so badly and was so sure of himself that we thought he had the whole package to be a full first-team player.
"In England he gets the challenge he needs to grow. Manchester United is the absolute top. He will have to show it and must make this step to be important with the Oranje."