A brace from the Belgian was the highlight of a comprehensive rout by the hosts, which sends the Eindhoven outfit back into the title race following Twente's stumble
The sides were level on points at kick-off, trailing first-placed AZ by four points. Neither team had recorded a win in their previous domestic outing, meaning both needed a victory to keep their title-aspirations alive.
Relieved of European duty following their Europa League elimination at the hands of Valencia and with all eyes on national glory, it was the hosts who got off to a flying start. In-form Toivonen again provided the inspiration, curling a terrific effort past Vandenbussche after Strootman had found his skipper in space.
The Swede should have made it two 11 minutes in, after a perfectly weighted cross from Lens had left the midfielder with only the keeper to beat. The home fans were on the edge of their seat again just minutes later, when Strootman’s acrobatic effort bounced agonizingly wide of the post.
The home side continued to dominate proceedings, looking crisp in possession while coping with the visitors’ notorious wingmen. Strootman saw a powerful effort fly wide, before Matavz spurned a good chance in similar fashion. Lucido Narsingh then spurned his side’s best chance of the half seven minutes from time, when the Dutchman fired over with only Tyton standing between him and an equalizer.
Both sides came out of the break with offensive intentions, but neither had the incisiveness to forge any chances of note until PSV clumsily conceded an equaliser in the 51st minute. Viktor Elm sent the ball towards Tyton, who blocked the attempt only to see Pieters fumble the ball over his own line.
Heerenveen were given little time to enjoy their equalizer however, with Mertens restoring his side’s lead just five minutes later. The Belgian ominously cut in from the left flank, before lashing a thunderous effort into the back of the visitors’ net.
Wijnaldum was presented with a golden opportunity to net his side’s third shortly after. Mertens found the Dutch international in the box with an immaculate delivery, but the midfielder sent header straight at Vandenbussche. The keeper only palmed away the effort, but Wijnaldum was unable to convert the resultant chance.
The hosts would net be denied a third however, with the game-clincher coming from an unlikely source. Lens sent a slicing pass through to substitute Engelaar, who coolly chipped the Heerenveen keeper to net only his first goal of the season.
And Heerenveen’s misery did not end there, as the Friesian outfit conceded a fourth minutes later. Goalscorer Mertens stylishly added his second of the night after being sent into space, calmly lobbing the ball over a charging Vandenbussche.
The rout was completed in the 85th minute, when Depay converted a sumptuous delivery from Strootman. The Dutchman found the youngster at the end of another blistering counter, and the forward coolly slotted home his first goal for the senior side.
The crucial win leaves PSV, provisionally, within touching distance of AZ, with just one point separating the title rivals. Heerenveen meanwhile lose footing in the title race, and now find themselves seven points off the league summit.