A brace from South Korean forward Suk Hyun-Jun and a Leandro Bacuna goal helped Groningen to the convincing home win.
AZ Alkmaar 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.
Elsewhere, Twente crushed Vitesse 4-1 with Leroy Fer, Luuk de Jong, Ola John and Nacer Chadli all netting.
