Eredivisie leaders Feyenoord dropped points on a weekend when second-placed Ajax drew and PSV, in third, comfortably won.
Mathias Pogba scored the only goal of the game for struggling Sparta Rotterdam in their clash with Feyenoord after just one minute, to aid their battle for survival, in 14th.
The result left the league leaders now just four points ahead of Ajax – who drew with Groningen.
Brian Linssen had scored on 56 minutes for the 11th-placed Groningen before Davy Klaassen netted an equaliser with 82 minutes played.
PSV had kept up their title-challenge with a 4-0 rout of Roda JC on Saturday.
AZ, in fifth, meanwhile, were held to a 1-1 with Excelsior.
Warner Hahn put the ball into his own net on 20 minutes with Mike van Duinen netting an equaliser on the hour mark.
Excelsior moved up into 16th, with 20 points from 25 games.
Bottom-side ADO Den Haag were involved in a similar upset when they held fourth-placed Utrecht to a 1-1 draw.
Dion Malone had put the home side ahead on just 16 minutes but they failed to build on that goal as Richairo Zivkovic drew level five minutes before half-time.
In the day's late game, NEC defeated Heracles 3-1 with goals from Julian von Haacke (27), Michael Heinloth (33) and an own-goal from Justin Hoogma (69) where Samuel Armenteros had opened the scoring for the visitors from a 14th minute penalty.
Heracles ended the weekend in 10th with 28 points, with NEC on 25 points in 13th.
All the results in full:
AZ 1-1 Excelsior
Sparta Rotterdam 1-0 Feyenoord
Groningen 1-1 Ajax
Utrecht 1-1 ADO Den Haag
NEC 3-1 Heracles