Ajax's Anwar El Ghazi scored twice in a 4-0 win over ADO Den Haag that took them clear at the top of the Dutch league on Sunday.
There were wins for Ajax and Feyenoord in the Eredivisie on Sunday, while FC Twente slipped to defeat.
Ajax started their Eredivisie campaign with victory over AZ Alkmaar, while Willem II and Vitesse played out a 1-1 draw.
Watford have completed the signing of Steven Berghuis from AZ Alkmaar.
Watford are set to make AZ Alkmaar forward Steven Berghuis their 10th signing of the summer.
Marco van Basten is returning to the Netherlands back-room staff as assistant to new coach Danny Blind.
Marco van Basten talks Sacchi, Michels and Cruyff, and why he walked away from management.
AZ claim a Europa League place at the expense of Feyenoord, who were consigned to the play-offs for a place in Europe.
Eredivisie champions PSV Eindhoven have made Danish defender Simon Poulsen their first signing of the summer.
NAC Breda face a relegation play-off, while Manchester United-bound Memphis Depay scored for PSV.
AZ Alkmaar remain in contention to clinch a Europa League berth from the Eredivisie after a 2-0 win at FC Twente.
Champions Ajax delayed PSV's impending Eredivisie title win for another week as they won 2-0 away at Heracles Almelo.
Ajax lost more ground on Eredivisie leaders PSV Eindhoven after they were held to a 1-1 draw by Utrecht.
Markus Henriksen netted a late winner as AZ strengthened their grip on fourth place with a 2-1 win over Cambuur Leeuwarden.
Vitesse claimed their seventh Eredivisie win in eight matches but left it late to beat AZ Alkmaar 3-1.
AZ Alkmaar had to overcame blustery conditions to beat Willem II 2-0 to reclaim third place in the Eredivisie on Saturday.
Luuk De Jong scored a hat-trick as PSV strengthened their grip at the top of the Eredivisie after a 4-2 victory at AZ.
A calamitous error by Go Ahead Eagles goalkeeper Mickey van der Hart gave parent club Ajax a 2-1 win.
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.