Feyenoord's UEFA Champions League hopes were dealt a blow as they lost further ground on second-placed Ajax after going down 2-0 at relegation-threatened Heracles.
Fred Rutten's men could have moved to within two points of Eredivisie champions Ajax with a win at the Polman Stadion.
However, the visitors fell behind on the stroke of half-time when Bryan Linssen took advantage of some slack Feyenoord defending to hit a wonderful curling half-volley over a stranded Kenneth Vermeer.
Thomas Bruns then powered home a header five minutes from time to lift Heracles to 15th, while Feyenoord will go eight points behind Ajax if Frank de Boer's side win at home to Twente on Sunday.
A Demy de Zeeuw double was not enough for NAC Breda, as they went down 3-2 at ADO Den Haag.
Michiel Kramer scored in between De Zeeuw's two goals, with Xander Houtkoop again levelling for the hosts in the 76th minute.
And so it was left to Kramer to net the winner five minutes from time, moving Den Haag four points clear of the relegation play-off spots.
Elsewhere, Excelsior and Groningen played out a 1-1 draw, while Vitesse beat Willem II 2-0.