Battling Barnsley were left heartbroken after a thrilling end at Wolves.
Adam Jackson had seemingly earned the Reds a deserved point with his 90th-minute equaliser - after Bright Enobakhare's opener.
But right at the death the hosts stole the spoils through Alfred N'Diaye.
It was a chalk and cheese performance from the one that saw the Reds batter the toothless Wolves 4-0 the last time the two sides met at Molineux.
But both sides have moved on since then, with the hosts spending big in the summer transfer window.
Jackson capped a fine defensive display with a goal but that wasn't enough for a point.
Paul Heckingbottom said he wanted the Reds to build on their resolute performance from Wembley in midweek and they did just that for the most part.
Adam Davies came close to keeping a fitting clean sheet on his 100th consecutive appearance, but it wasn't to be.
Jackson also put in a real shift in the heart of the defence, and popped up with the goal late on.
Both sides made a slow start to the contest, with Tom Bradshaw having the first real chance when he headed at John Ruddy.
On the half-hour mark huge appeals for a Reds' penalty were turned away when Bradshaw was bundled over in the box.
Ivan Cavaleiro should have scored when he missed the target with a close-range volley.
Late in the half Adam Hammill forced Ruddy into a top stop to keep the game goalless.
The Reds had to hold on early into the second period as Wolves pushed hard.
Jackson continued his brick wall performance at the back with a couple of great tackles.
Jackson missed a great effort himself before substitute Ryan Hedges had a strike blocked.
Ten minutes from time Enobakhare volleyed home the opener at the back post.
And with the Reds destined for defeat Jackson seemingly stole a point with a cracking strike of his own.
But in the dying embers Reds fans were left distraught when N'Diaye beat Davies.