Ajax maintained their three-point advantage over Feyenoord with a 1-1 away draw on Sunday, as PSV Eindhoven jumped into second spot.
Feyenoord lost ground in the Eredivisie title race after a shock 1-0 loss against ADO Den Haag.
There were Eredivisie wins for both Ajax and PSV on Saturday, while second-placed Heracles slipped to defeat.
Heracles Almelo moved to the top of the Dutch league with a 2-1 win over champions PSV Eindhoven at the Polman Stadion on Saturday.
Wout Weghorst scored the only goal as high-flying Heracles beat ADO Den Haag 1-0 to climb to second in the Eredivisie.
Feyenoord and Roda JC secured opening day victories in the Eredivisie.
AZ claim a Europa League place at the expense of Feyenoord, who were consigned to the play-offs for a place in Europe.
NAC Breda face a relegation play-off, while Manchester United-bound Memphis Depay scored for PSV.
PSV came from behind to extend their lead at the top of the Eredivisie standings, while there were wins for Heracles and Utrecht
After the title was taken away from them on Saturday, Ajax were held by struggling NAC Breda at home on Sunday.
Feyenoord moved a step closer to qualifying for the Europa League after a 2-2 draw at Willem II Tilburg in the Eredivisie.
Ajax lost more ground on Eredivisie leaders PSV Eindhoven after they were held to a 1-1 draw by Utrecht.
It was a day to forget for Utrecht defender Ramon Leeuwin as he scored an own goal and was sent off against Ajax.
Cash-strapped Twente Enschede returned to winning ways in the Eredivisie on Saturday with a 2-0 win over PEC Zwolle.
Ajax staged a late rally to beat PSV Eindhoven 3-1 on Sunday to give their faint title hopes a boost.
Ricardo Kishna struck twice as Ajax beat Twente 4-2 in the Eredivisie to cut PSV's Eredivisie lead back to 12 points.
Stefan Nijland scored in each half as PEC Zwolle moved up to third with a thumping 4-0 win at bottom side Dordrecht.
Ajax lost 1-0 at Vitesse Arnhem on Sunday to fall further behind PSV in the Eredivisie title race.
Feyenoord beat FC Twente to strengthen their hold of third place in the Eredivisie on Sunday, while Heerenveen won at Utrecht.
PEC Zwolle moved up to fifth in the Eredivisie as they beat ADO Den Haag 3-1 and FC Twente drew 2-2 against Vitesse.