Stam gave the 17 year-old his debut as PEC Zwolle boss.
"We all know how this world works, so it's inevitable that a player makes a transfer at a certain point in his career.
"We know that English and Spanish clubs scout all over the world, but especially in the Netherlands for talented Dutch defenders, because they're known to be good with their feet.
"Those clubs usually have enough money lying around to take a risk and sign a few of them and see if it pays off in the long run.
"If it works out, great. If it doesn't, they'll probably sell them for more money than before. In the end it's up to the clubs, but I wish Sepp all the best and I hope he'll turn out to be a big success story at Liverpool."