Eredivisie wrap: Shock losses for PSV, AZ
Top sides PSV Eindhoven and AZ Alkmaar both suffered shock defeats in the Eredivisie on Sunday, while Ajax were victorious.
Groningen moved into eighth after a surprisingly comfortable 3-0 win over Fred Rutten's top-of-the-table PSV.
A brace from South Korean forward Suk Hyun-Jun and a Leandro Bacuna goal helped Groningen to the convincing home win.
The hosts took a 29th-minute lead when Suk played a one-two with Petter Andersson before striking into the bottom corner from a narrow angle.
A superb counter-attack had them 2-0 up, with Bacuna placing home from the edge of the area after a neat Dusan Tadic pass.
PSV's hopes of getting anything out of the encounter took a blow just before the hour-mark when Bulgarian Stanislav Manolev was adjudged to have dived and consequently given his second yellow card.
Groningen wrapped up their win when PSV goalkeeper Andreas Isaksson only partially cleared a weak Zakaria Labyad back pass and Suk lobbed the shot-stopper from distance.
But PSV remain top after AZ Alkmaar, who are second on goal difference, suffered a 3-0 defeat at Utrecht.
Alexander Gerndt struck from the penalty spot after Niklas Moisander was sent off on 15 minutes, before the Swedish attacker netted a second.
Edouard Duplan made it 3-0 after 41 minutes, putting an end to the contest before the half-time break.
A comfortable 4-1 win over NEC Nijmegen sent Ajax into fifth spot.
Dmitri Bulykin hit a first-half brace as Jan Vertonghen and Siem de Jong also got on the scoresheet at Amsterdam Arena.
Rens van Eijden struck a 69th-minute consolation goal for the visitors, who are just four points clear of the relegation playoff spots.
Elsewhere, Twente crushed Vitesse 4-1 with Leroy Fer, Luuk de Jong, Ola John and Nacer Chadli all netting.
Twente had Peter Wisgerhof sent off after 80 minutes with Wilfried Bony missing a spot-kick for Vitesse, who pulled a goal back late in the encounter courtesy of substitute Mike Havenaar.