PSV were 2-0 winners at home against RKC Waalwijk to go two points clear at the top, while Vitesse thrashed ADO Den Haag 4-0 to join Ajax in a share of second on 54 points.
Ajax were facing a tricky Sunday trip to face an AZ Alkmaar side who last month knocked them out of the KNVB Beker with a stunning 3-0 win in Amsterdam.
An early goal settled PSV against RKC, with Dries Mertens converting a sixth-minute penalty, and Georgino Wijnaldum added the second goal in the 69th minute, a sweet chip from 15 yards.
Vitesse were impressive winners away from home, with Wilfried Bony netting after eight and 39 minutes to leave ADO with it all to do in the second half.
Marco van Ginkel added the third goal after 55 minutes and Mike Havenaar compounded the pain for the hosts with a fourth in the 84th minute.
Struggling VVV Venlo remain firmly embedded in the relegation picture after a 2-0 home defeat against Heracles. Everton scored the first after 61 minutes and Mike te Wierik followed it up six minutes later.
In-form Heerenveen came from behind to snag a 3-1 win at fellow mid-table outfit NEC Nijmegen.
Ruud Boymans set them on the back foot with a 62nd-minute opener, but Alfred Finnbogason levelled eight minutes later and it took only a further three minutes for Filip Djuricic to nudge Heerenveen in front. Djuricic added his second in the 90th minute.