By Peter ORourke. Last Updated: January 1, 1970 1:00am
Ajax lost further ground on the leading pack after a surprise 1-0 defeat to NEC Nijmegen.
The Dutch giants were undone by a 52nd minute goal by Romano Denneboom to inflict their fourth defeat of the season on Danny Blind's men.
The defeat leaves Ajax a massive 13 points behind leaders PSV Eindhoven.
Feyenoord missed the chance to move into second after being held to a disappointing goalless draw by Vitesse at De Kuip.
Heerenveen climbed into seventh spot with a thumping 4-0 win over Groningen.
Klaas Jan Huntelaar set the home side on their way with the opener after just five minutes and former Manchester City midfielder Paul Bosvelt doubled the lead two minutes before the break.
Huntelaar made the game safe with his second two minutes after the break and Georgios Samaras completed the rout with the fourth on 74 minutes.
ADO Den Haag picked up a precious point in their battle against relegation with a 1-1 draw at Utrecht.
Robin Nelisse gave Utrecht the lead on 51 minutes, but former Rangers striker Michael Mols earned Den Haag a point with an equaliser four minutes later.
Click on fixture for full match summary