Three goals in each half disposed of mid-table Groningen to narrow the gap on Alkmaar who beat Utrecht 2-0 on Friday but still have a game in hand on PSV who have now played 14.
Belgium international Dries Mertens (pictured) was PSV's inspiration as he set up Kevin Strootman after 14 minutes to open the scoring before curling a free-kick round the wall to double the lead.
Zakaria Labyad and Georginio Wijnaldum settled the match for PSV and, after Nicklas Pedersen pulled one back for the visitors, Tim Matavz and Ola Toivonen completed the rout.
Alkmaar are top with 34 points ahead of PSV (31).
Heerenveen climbed to fourth on 22 points after grabbing a 2-2 draw at NAC Breda with right-back Darryl Janmaat getting the equaliser after 61 minutes following an impressive run.
Roda JC Kerkrade's Mads Junker hit a second-half double as they beat Heracles Almelo 3-1 to move up three places to 10th while Graafschap Doetinchem came from behind to overcome fellow strugglers VVV Venlo 2-1 with a late winner from Yuri Rose.
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