Mael de Gevigney was sent off in the third minute at leaders Birmingham City and Barnsley eventually lost 6-2.
The Blues took the lead from the penalty spot but Davis Keillor-Dunn levelled within a few minutes.
The hosts scored twice early in the second half and, after Stephen Humphry replied, added another three.
It was a gutsy first half display by the Reds who played with ten men for nearly the whole game but they also conceded some poor goals as they fell apart after the break.
They are now winless in seven and have taken just 12 points from their last 16, leaving them 12th in the League One table.
Conor Hourihane made three changes from the side that lost at home to Exeter on Tuesday. In came Adam Phillips, Luca Connell and Max Watters in place of Jonathan Bland, Fabio Jalo and Kelechi Nwakali.
They started off in a 4-3-3 with Conor McCarthy at left-back but soon had to change.
The Reds got off to the worst possible start as de Gevigney was sent off for bringing down Keshi Anderson following a long ball. Barnsley disputed it as Marc Roberts was covering so de Gevigney did not appear to be the last man.
The ten men nearly took the lead soon after when a right-wing corner was turned onto the post by former Birmingham man Marc Roberts.
Barnsley brought on Jonathan Bland for striker Max Watters, and he went to right-back with Corey O’Keeffe moving to the left.
Birmingham almost took the lead when Anderson shot badly wide unmarked from close range after a good run and cross by Kieran Dowell then Ethan Laird easily beat O’Keeffe in the air but blasted over from the right of the box.
Phillips forced a save out of Ryan Allsop from the edge of the box after Stephen Humphrys led a counter-attack and played him in.
O’Keeffe gifted the ball to Jay Stansfield whose shot was blocked then, at the other end, Humphrys went clean through on halfway and tried to chip the goalkeeper but did not get enough height and it was beaten away.
The Blues won a penalty when Dowell dummied a pass into the box and Anderson went through to be tripped by goalkeeper Kieren Flavell. Stansfield put the penalty into the bottom left corner as Flavell dived the correct way but could not get there.
Barnsley responded almost instantly with Keillor-Dunn’s header at the back post from a right-wing long throw bouncing in off Tomoki Iwata.
Phillips headed over at the back post from O’Keeffe’s cross after a good move down the left on the stroke of half-time.
The hosts retook the lead 90 seconds into the second half when Dowell’s right-wing corner was headed down by Roberts for Ben Davies to volley in from close range.
It was 3-1 on 56 minutes when a left-wing cross was missed by McCarthy and Alfie May headed home.
Barnsley replied on the hour when, after being found by a nice Phillips pass, Humphrys’ shot from a tight angle on the right was fumbled in by Allsop.
It should have been 4-2 when McCarthy slipped and gave the ball to May who burst into the box on the right and tried to square to Stansfield but Connell made a brilliant interception.
The hosts did score a fourth when substitute Luke Harris was put through by May and finished well.
Humphrys beat a couple of men and saw a 30-yard shot well-saved then Stansfield hit the post at the other end with a 25-yard strike before May fired over from closer in.
The fifth goal saw May lead a counter-attack and play in Dowell who beat McCarthy and Bland before finding the bottom right corner from the edge of the box.
For the sixth, substitute Nwakali lost the ball in his own half to Dowell and home sub Lukas Jutkiewicz went clean through then, after Flavell saved his first attempt, he tapped into the empty net.
Barnsley (4-3-3): Flavell; O’Keeffe (Lembikisa 86mins), de Gevigney, Roberts, McCarthy; Phillips (Jalo 72mins), Connell (Nwakali 86) Russell; Keillor-Dunn, Watters (Bland 7), Humphrys (Lewis 86).
Unused: Hayton, Barratt.
Red card: de Gevigney.
Yellow cards: Bland.
Goals: Keillor-Dunn 32, Humphrys 60.
Birmingham (4-2-3-1): Allsop; Laird (Sampsted 66mins), Klarer, Davis, Cochrane; Paik, Tomoki; Dowell, Willumsson (May 37), Stansfield, Anderson (Harris 66).
Unused: Peacock-Farrell, Hanley, Leonard, Jutkiewicz.
Yellow cards: Klarer.
Goals: Stansfield 33 (pen), Davies 47, May 56, Harris 73, Dowell 82, Jutkiewicz 89.
-
-
3:01pm
-
3:02pm
-
3:03pmRED CARD
-
3:05pm
-
3:05pm
-
3:06pm
-
3:07pm
-
3:07pm
-
3:09pm
-
3:09pm
-
3:11pm
-
3:12pm
-
3:12pm
-
3:12pm
-
3:16pm
-
3:16pm
-
3:17pm
-
3:18pm
-
3:18pm
-
3:19pm
-
3:19pm
-
3:21pm
-
3:22pm
-
3:23pm
-
3:23pm
-
3:25pm
-
3:27pm
-
3:28pm
-
3:29pm
-
3:31pm
-
3:31pm
-
3:32pm
-
3:32pm
-
3:33pmGOAL!
-
3:35pmGOAL!
-
3:37pm
-
3:37pm
-
3:40pm
-
3:42pm
-
3:45pm
-
3:45pm
-
3:47pm
-
3:48pm
-
3:51pm
-
3:51pm
-
3:52pm
-
3:53pm
-
4:09pm
-
4:10pm
-
4:12pmGOAL!
-
4:14pm
-
4:14pm
-
4:15pm
-
4:17pm
-
4:19pmGOAL!
-
4:20pm
-
4:22pm
-
4:23pmGOAL!
-
4:25pm
-
4:25pm
-
4:28pm
-
4:29pm
-
4:29pm
-
4:30pm
-
4:30pm
-
4:31pm
-
4:32pm
-
4:35pm
-
4:35pm
-
4:35pm
-
4:36pm
-
4:36pmGOAL!
-
4:38pm
-
4:38pm
-
4:40pm
-
4:43pm
-
4:44pm
-
4:45pm
-
4:46pmGOAL!
-
4:48pm
-
4:50pm
-
4:52pm
-
4:54pmGOAL!
-
4:55pm
-
4:59pm