Rochdale 3 (Andrew 8, Vincenti 36, Henderson 63)
It was evident that Barnsley's midweek Cup heroics had taken their toll as a tired and leggy performance at Rochdale saw them slip to a disappointing 3-0 defeat.
There was little action in the opening five minutes although Conor Hourihane's late challenge from behind on Henderson.
However on eight minutes, the home side took the lead out of nowhere. When the ball dropped kindly for Calvin Andrew on the edge of the box, he thumped at goal with Davies getting a hand to it but the ball found the top corner.
When Mawson's pass infield for Pearson went astray, Andrew picked up possession before unleashing vicious drive that, thankfully, Pearson blocked with 16 played.
Barnsley were contributors to their own downfall as careless passing in their own third saw Henderson have a free shot at goal that went wide on 20 minutes.
The best the Reds could offer was a wayward shot from Pearson that bent out for a throw-in on 28 minutes. At the other end McDermott went close with a fizzing low shot that went the wrong side of Davies' left-hand post.
Harris was proving to be Barnsley's best threat and was giving Tom Kennedy a torrid time. After beating him down the right on 33 minutes, Harris curled a decent effort with his left boot but couldn't direct his shot on target.
It got worse for the Reds on 36 minutes as a Rochdale corner evaded the arm of Davies, allowing Peter Vincenti a free header that hit the net for 2-0.
Lee Johnson opted for two changes in the second half with Sam Winnall and Dan Crowley replacing Conor Wilkinson and Joe Rothwell as the Head Coach looked to shake up the tired-looking Reds.
Both sides saw decent crosses cleared by their respective defences. Harris for the Reds beat McNulty before his delivery for Mawson was hacked away. Mawson himself was on hand at the other end on 51 minutes to smash clear following Henderson's pull-back.
Harris robbed Kennedy on the right with 57 played before slipping Winnall into the box. The forward found the angle too tight, however, and his cross was easily cleared.
Moments later at the other end, Peter Vincenti had a free header straight at Davies as the game stretched heading towards the hour mark.
The game was practically put beyond reach on 63 minutes when Ian Henderson's smart finish made it 3-0. Allen's push on Hourihane went unpunished and the Dale captain raced towards goal before sliding the ball into Henderson to finish.
Three minutes after the third goal, George Smith replaced Lewin Nyatanga for Barnsley's final substitution.
Calvin Andrew should have had his second and Rochdale's four on 68 minutes but for a very smart save by Adam Davies. His low strike from 15 yards was well saved by the legs of Barnsley's number one.
Josh Lillis was forced into his first save of the match on 72 minutes as good play between Crowley and Watkins saw the latter find Pearson to strike from 20 yards, with Lillis tipping away for a corner.
The latter stages of the game just drifted away for the Reds as they failed to really trouble Lillis in the Rochdale goal.
Rochdale: Lillis, Rafferty, McNulty, Lancashire, Vincenti (Bunney 75), Andrew, McDermott (Noble-Lazarus 84), Allen, Cannon, Kennedy, Henderson.
Subs: Eastham, Alessandra, Collis, Rose, Camps.
Reds: Davies, Wabara, Roberts, Nyatanga (Smith 66), Mawson, Harris, Pearson, Rothwell (Crowley 46), Hourihane, Wilkinson (Winnall 46), Watkins.
Subs: Walton, Scowen, Maris, Digby.
Refere: G. Sutton.
Attendance: 3,618 (1,295 Reds)