Van Persie was today being examined by the Feyenoord doctor for head and neck injuries. His Chilean team-mate, Jorge Acuna, spent the night in hospital with concussion and bruises.
Feyenoord youth trainer Mario Been said: "My players were hit, kicked, and I was threatened with a knife. It's too crazy for words."
Scouts from Tottenham, Arsenal and Manchester United were at last night's match in a mini-stadium next to the Amsterdam Arena for what was essentially a national Under-21 championship match.
The game would normally have only been watched by a few dozen people, but because of the presence of first team regulars such as Van Persie, 4,000 fans attended the match.