Barnsley slipped into the relegation zone after they suffered a fifth straight League One defeat at home to lowly Fleetwood Town on Saturday.
The Cod Army took advantage of a Paul Digby error to take the lead after 29 minutes and the Reds created very few chances in their pursuit of an equaliser.
Barnsley now have 14 points from as many games and have fallen to 21st, one place below Fleetwood.
Lee Johnson made four changes to the team that started the 2-0 loss to Walsall four days previously. Lloyd Isgrove, who signed earlier in the day from Southampton, was brought in along with fellow winger Kadeem Harris as well as Dan Crowley and Digby, who made his first start of the season. Dropping out were experienced defender Lewin Nyatanga as well as strikers Michael Smith and Simeon Jackson and the suspended central midfielder Ben Pearson.
Fleetwood were gifted the lead after a quiet first half hour in which Crowley and Josh Scowen both failed to test visiting 'keeper Chris Maxwell with long-range shots after home stopper Nick Townsend had comfortably held two efforts in the first minute.
The Reds looked nervous on the ball at the back and that proved their undoing when Digby miscontrolled a pass in front of his goal and Jamie Proctor outpaced the home defence then finished well past Townsend to make it 1-0 to the visitors.
Barnsley captain Alfie Mawson came closest to levelling before the break as he headed George Smith's free-kick just over the bar then sent a free-kick of his own towards the top left corner but it was clawed out well by Maxwell.
Johnson made a double change at the break with Nyatanga replacing the booked Marc Roberts at centre-back and Michael Smith coming on to partner Sam Winnall up front at the expense of Crowley as the Reds reverted from 4-5-1 to 4-4-2.
Michael Smith's header from Isgrove's cross was saved by Maxwell at full-stretch diving to his right then, at the other end, Richard Wood's header was blocked on the line by Townsend.
Third substitute Simeon Jackson fired over late on with a wayward shot which summed up a disappointing display from the Reds.
