Markus Henriksen netted a late winner as AZ strengthened their grip on fourth place with a 2-1 win over Cambuur Leeuwarden.
Defender Nicolas Isimat-Mirin scored a rare goal to hand leaders PSV a nervy 2-1 home win over Groningen.
AZ Alkmaar had to overcame blustery conditions to beat Willem II 2-0 to reclaim third place in the Eredivisie on Saturday.
Feyenoord slipped 20 points behind leaders PSV in Eredivisie after a 2-0 defeat at lowly Heracles on Saturday.
AZ Alkmaar inflicted a second league defeat in four days upon Ajax as they registered a 1-0 win at the Amsterdam ArenA.
Ajax lost 1-0 at Vitesse Arnhem on Sunday to fall further behind PSV in the Eredivisie title race.
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