Vitesse slipped to a 2-0 home defeat to AZ on Tuesday, bolstering Ajax’s hopes of a fourth straight Eredivisie title.
Peter Bosz’s side could have leapfrogged the league leaders with a victory, but instead the initiative has been handed to Ajax, who can move five points clear of Vitesse if they beat Groningen on Thursday.
Two first-half goals proved to be enough for 2008-09 champions AZ to claim the points, the first coming as Vitesse defender Patrick van Aanholt turned the ball into his own net after 20 minutes.
Striker Aron Johannsson secured the win three minutes before half-time with his 13th league goal of the season, the American coolly lofting the ball over Vitesse goalkeeper Piet Velthuizen.
Fourth-placed Feyenoord remain in the title race following a 2-1 success at relegation threatened Roda JC.
Ronald Koeman’s men looked to be in command after first-half goals from midfielder Lex Immers and Swedish attacker Samuel Armenteros.
But the hosts battled back in the second half and got back into the game thanks to a 77th minute penalty from midfielder Anouar Kali.
Roda could not complete the comeback, though, as Feyenoord held on to move within four points of Ajax.
Elsewhere, Heracles are now six points clear of the relegation play-off zone thanks to a comfortable 3-0 win over bottom club ADO Den Haag.
Attacker Bryan Linssen opened the scoring inside two minutes, before a double from on loan Heerenveen striker Mark Uth wrapped things up for the visitors.