The Reds were beaten 3-0 for the second time in five days as they sank to the bottom of the Championship at Watford's Vicarage Road on Saturday.
A disastrous start saw Watford go two goals up inside 16 minutes. Cristian Battocchio fired into the top corner from 25 yards for a superb sixth-minute opener after Barnsley captain Stephen Dawson made a mess of a clearance. The Reds were then brutally exposed by a Watford move that finished with Troy Deeney having yards of space to turn and fire home inside the box.
It seemed as if the Hornets would run riot as Luke Steele had to produce outstanding saves from Davide Faraoni between the two goals.
But the match quitened down after that although Alexander Merkel made it 3-0 from close range on 75 minutes. Barnsley's best chance came late on when Nick Proschwitz hit the bar with a lob after a superb Jacob Mellis pass.
Manager Danny Wilson made five changes to the side that were beaten 3-0 at home to Leicester on Tuesday as injured centre-backs Martin Cranie and Peter Ramage were replaced by Lewin Nyatanga and Jean Yves M'voto. Liam Lawrence and Emmanuel Frimpong came in for Martin Woods and Paddy McCourt while Proschwitz was preferred up front to top-scorer Chris O'Grady who eventually came on after 60 minutes along with youngster Reuben Noble-Lazarus.
The goalless draw between Millwall and Charlton meant the Addicks moved above the now bottom Reds but that the fourth-bottom Lions are still only three points ahead of them.