It's a bad day at the office for Gerhard Struber and his Reds side, thumped away from home by relegation rivals Stoke City.
The battle to remain in the Sky Bet Championship became a whole lot harder for Barnsley with this display at the Bet365 Stadium.
Stoke went into the half time break three goals to the good, and a second half rocket from Tom Ince sealed an emphatic victory for the Potters.
Gerhard Struber had made three changes for this one, and reverting to four at the back using the diamond. So there were starts for Luke Thomas, Kilian Ludewig and Conor Chaplin, with Jordan Williams, Elliot Simoes and the injured Romal Palmer making way.
It was a very nervous start from the Reds, who had all of the possession but were continually passing it up with cheap balls into midfield. They escaped any punishment, until a routine corner kick on eight minutes was met by Sam Vokes at the near post who easily rose above his man to nod beyond Jack Walton for 1-0.
The lead was doubled by Stoke on 10 minutes as Tyrese Campbell capitalised on a weak header in defence to make it 2-0 and leave Barnsley up against it with 80 minutes still to play.
It wasn't until the 23rd minute that Barnsley registered an attempt of note. Some good link-up play by Cauley Woodrow and Chaplin released Ludewig on the right of the box but his shot was parried behind by ex-Reds loanee goalkeeper Jack Butland.
The hosts made it 3-0 on 38 minutes when another corner routine confused the Reds defence and Campbell stroked home from 12 yards.
It might have been 4-0 but for an excellent diving save from Walton to deny Vokes a second just before half time.
HALF TIME: Stoke 3-0 Reds
Struber made a treble change during the interval, with Ben Williams, Marcel Ritzmaier and Jacob Brown replaced by Jordan Williams, Callum Styles and Simoes. But nothing altered for the visitors, who huffed and puffed.
There was a Woodrow free-kick skying the crossbar from the edge of the box, Mowatt had his own effort that stung the hands of Butland, and there was lots of neat stuff in the middle of the park, but very little that looked likely to threaten Stoke who just sat in with 10 men behind the ball.
Clarke Oduor and Patrick Schmidt made appearances in that second half, but their impact was minimal. And it was the home side who finished the strongest.
Nick Powell saw a driving effort tipped behind by Walton late on, and the fourth goal arrived when substitute Ince, on the pitch for barely a minute, picked up the ball inside the box without a defender near him and rocketed home to condemn Barnsley to their biggest defeat of the season under Struber's stewardship.
A really bad day at the office for Barnsley who now slip four points adrift of safety with this damaging defeat against their nearest relegation rivals, who completed a league double over the Reds in the process.
FULL TIME: Stoke 4-0 Reds
Walton, Ludewig (Oduor), Sollbauer, Andersen, B.Williams (J.Williams), Brown (Simoes), Mowatt, Thomas, Chaplin, Woodrow (Schmidt), Ritzmaier (Styles).