Lerin Duarte netted after six minutes for Heracles and they also hit the woodwork twice.
South Korean international Park, recently signed from Queens Park Rangers, then came off the bench to score in his first PSV appearance since his last spell at the club in 2005.
PSV, whose starting lineup did not feature a single foreigner in a rarity for Dutch football, had won their first three matches of the season but rested several players with an eye on their Champions League playoff at AC Milan on Wednesday.
Roda JC Kerkrade are fifth after a 4-0 rout of ADO Den Haag while NEC Nijmegen, who fired coach Alex Pastoor last week, let a two-goal lead slip to draw 2-2 with RKC Waalwijk.
(Reporting by Mark Gleeson in Johannesburg; Editing by Tony Jimenez; mark.gleeson@thomsonreuters.com +27828257807 Messaging mark.gleeson.thomsonreuters.com@reuters.net)
