The 22-year-old’s second goal rounded off a miserable afternoon for Palace as their three-man defence struggled to cope with a fluid and speedy Huddersfield outfit. Ward’s own goal and then a thumping header by Mounie within two first-half minutes gave the Eagles a sucker punch from which they could not recover.
Palace defended poorly for all three goals and looked vulnerable throughout as De Boer began his reign as Eagles manager with a 3-4-3 formation that on first evidence may incur some teething problems.
Scott Dann should have halved the deficit moments before Mounie settled the contest 12 minutes from time, the 30-year-old blazing over his six-yard effort before Huddersfield broke down the other end.
Despite their wretched defending, Palace wasted some good opportunities with Wilfried Zaha and Christian Benteke failing to convert chances albeit with Huddersfield goalkeeper Jonas Lossl making a fine save from the Belgian’s eight-yard header on the hour mark.
Zaha should have opened his account for the season before half-time when the 24-year-old beat two defenders in a flash but dragged his effort wide. Benteke put a header wide on the stoke of half-time from a Patrick van Aanholt corner.
The opening goal came from a poorly defended corner when Christopher Schindler rose highest to glance on Kasey Palmer’s inswinging delivery before Danish defender Zanka’s prod at the back post was bundled in by the wrong-footed Ward.
Palace had barely settled themselves when Aaron Mooy dug out a cross on the left wing and Mounie buried his header into the top corner with the Eagles’ defence static.
Andros Townsend was brought on at half-time for Luka Milivojevic as De Boer attempted to inject further pace into the Palace side. And the 26-year-old almost had an immediate impact when his low cross flashed across the box but was too long for the onrushing Benteke and Zaha.
Chelsea loanee Ruben Loftus-Cheek improved on his debut when he was switched to central midfield after half-time with some surging runs and his through ball nearly played in Zaha who was denied by the tenacious Huddersfield defence.
The game petered out in the afternoon sunshine and the third goal confirmed an embarrassing defeat for Palace before time was called on a disappointing afternoon for De Boer and co.