Huistra advised Groningen to sign Van Dijk as a 20-year-old in 2010 after watching him in a youth game for boyhood club Willem II, just months before he would arrive to take over as the Eredivisie side's manager.
He told the Daily Express: "I'm biased.
"But I think he is one of the best in the world at this moment."
Huistra added: "I told the Groningen technical director that he was a good player, a very interesting player.
"He still had to grow a little bit in terms of muscle. He was a bit lanky at the time and you could see he was not fully developed. But he certainly had some qualities.
"He was a good passer especially and had good defensive positioning.
"The older players immediately accepted him as a full member. Sometimes you have players from the reserves coming over and you still see some resistance with the older guys - but he was fully accepted from day one."