Belgian defender Mertens was part of the FC Utrecht backline that held the Partenopei to a goalless draw in a Europa League group game in Italy two years ago.
But Walter Mazzarri's men gave an early indication of the slick side they would become by rallying from two goals down to secure a 3-3 draw in the return fixture in Holland.
Edinson Cavani hit a hat-trick that night and, ominously, was on the plane that landed in Eindhoven today.
The Uruguay international has scored six goals so far this term as Napoli vie with Juventus for top spot in Serie A, but Mazzarri is expected to rest most of his regular starters on Thursday night.
Mertens, now a firm fixture in the PSV defence, told the club's official website: "Their personnel has changed slightly over time, but the team still plays the same way.
"When the opposition is on the ball, they play with five defenders but when they're on the ball they only use three.
"So on balance it's probably better that we keep the ball."
Now in his second spell at the Philips Stadion after a 14-year absence, Advocaat agreed with his players' tactical assessment.
"They start all bunched up together but then break away quickly," the 65-year-old said. "There are always a few players lurking up front who will kill you off."
Whether or not Mazzarri fields a perceived second-string team in Eindhoven is of no concern to the veteran Dutchman.
He added: "It will be a very good team anyway.
"We need to get a good result and I expect a motivated PSV."
Napoli have had a flying start to the season but coach Mazzarri knows they cannot afford to take their foot off the pedal.
He said: "In football today you cannot relax, even the coach, or you risk being made to look foolish against anyone.
"PSV are strong and we know that tomorrow's match is going to be very hard."