Rovers played their second South Yorkshire derby of the week hoping to end a run of five consecutive defeats.
Gareth Taylor, Lewis Guy and James Coppinger came back into the side that was beaten in midweek.
Doncaster had a great record at Oakwell in recent years and it looked like continuing when Brian Stock put Rovers ahead from the penalty spot in the eleventh minute.
The Rovers controlled the rest of the first half with Barnsley only ever getting the odd chance to test Sullivan in goal.
The second half started much the same as the first ended, within the first five minutes of the half though the incident happened that was to change the game.
Richie Wellens put Lewis Guy through and ex Rovers favourite Darren Moore pulled the Rovers striker back. Although still a long way from goal the referee had no hesitation in pulling out the red card and sending Moore off.
Within five minutes Barnsley were level, after some poor defending from a free kick Steve Foster was allowed a free header which somehow went through Matt Mills and into the net.
Before the goals the Barnsley fans were getting restless and the pressure was mounting on the Barnsley player and manager.
Just past the hour mark Jamal Campbell-Ryce picked the ball up for Barnsley well in his own half, after twisting Brian Stock in and out he then waltzed past another two Rovers defenders before shooting. What looked a routine save for Sullivan somehow got past him and into the Rovers goal.
Barnsley were now totally in control and you would have thought they had the extra man.
Worse was still to come, within seconds of coming on Jon Macken was able to tap in to make it three after Sullivan could only parry an initial Barnsley shot.
The home side wrapped up the game with only three minutes left on the clock when Iain Hume curled in a great shot from the edge of the area to make it four.
The defeat for Rovers now sends them into the bottom two.
A game which was Rovers for fifty minutes somehow changed completely when Barnsley went down to ten men.
With an international break next weekend Rovers now have a fortnight to work on their defensive and attacking frailties before entertaining Blackpool.
Join Vital Doncaster Rovers
Join Vital Doncaster Rovers!
With news and views, along with a forum, polls and article comments, everything you need in a fans site is right here!
You can even win prizes, by posting articles comments, posting on the message forum and voting on the polls.
Vital is also 100% interactive. Not only can you have your say on the articles and the forum but you can also suggest an article or a poll so you can air your views.
So why not join Vital today?
It’s easy to register here and enjoy getting involved
To visit the message board, click here.
This website is your website and we are looking for people to help run the site. Do you go to most of the games and have an opinion? Why not write a match report? Perhaps you are a budding journalist or even just someone who is very opinionated? Well why not join our team? If this interests you please contact Vital Doncaster .