Eleventh straight win puts Ajax on brink of title
Derk Boerrigter (pictured) broke the deadlock against struggling Groningen, who have lost 10 of their last 12 matches, netting after a Siem de Jong shot was blocked on the stroke of half-time.
De Jong also had a hand in the second goal, setting up Kolbeinn Sigthorsson 10 minutes before time to settle the match.
Ajax have 67 points with three matches remaining and need four more, starting next Sunday away at Steve McClaren's fourth-placed Twente Enschede who beat bottom side Excelsior Rotterdam 1-0 on Saturday to move to 60 points.
AZ Alkmaar and Feyenoord are joint second on 61 points after both registered 2-1 victories over VVV Venlo and ADO Den Haag respectively. They meet next Sunday in Rotterdam in their battle for second place which brings a place in the Champions League qualifiying round.
Brett Holman put Alkmaar ahead two minutes into the second but Quin Kruysen equalised from close range just before the hour mark. U.S. international Jozy Altidore restored the lead six minutes later with a well-placed header.
Feyenoord grabbed the lead early in the second half when Ruben Schaken notched in a cross from Guyon Fernandez who doubled the lead 20 minutes before time. Lex Immers converted a penalty a minute before time to pull one back.
PSV Eindhoven, fifth on 60 points, came from behind to beat NEC Nijmegen 2-1. Navarone Foor put Nijmegen ahead after seven minutes but midway through the second half Jetro Willems equalised before Jan Vennegoor of Hesselink netted a close range winner after 88 minutes.