Leyton Orient's unbeaten run came to a sorry end as they let a single-goal lead disappear in the final two minutes to 10-man Barnsley.
The O's had arrived at Oakwell on theback of six wins and two draws from their last eight games and looked to be about to add to that following Ruel Sotiriou's goal on 10 minutes.
But two goals from Adam Phillips, the first on 88 minutes and the second five minutes into stoppage time, gave the Tykes a 2-1 win.
They also came either side of Luca Connell's red card but Orient boss Richie Wellens was quick to dismiss any thoughts about bad luck going against his side.
"It’s not cruel when you sit deep and invite teams on," he said.
"I think first 20 minutes, half an hour we were very good. We went 1-0 up and every time we attacked we looked a real threat.
"Then we didn’t play with enough bravery to pass the ball, we didn’t play with enough bravery to switch the ball and everything we wanted to do.
"And the accumulation of not being brave enough and fatigue, especially in the last 10 to 15 minutes, has cost us the game.
"I don’t think we can begrudge them. I think they deserved to win the game because the pressure was building.
"Our game management was really, really poor and if you allow teams like this to build momentum and you never break it, then unfortunately you’re going to pay the price."
The Orient goal came after George Moncur drove to the byline and cut the ball back for Sotiriou to apply the finish.
But from there it was Barnsley who dominated possession and chances for the remainder of the game.
They could not find a way past an inspired Sol Brynn but he was finally beaten as he came to gather ball launched in behind the Orient defence.
Phillips flicked the header beyond him.
Connell was shown a second yellow card as he protested that Orient were taking too long to restart the game.
But despite the numerical disadvantage, Phillips won it for his side when he connected with Corey O’Keefe’s free-kick.
Orient's last defeat was away to another promotion candidate in Bolton Wanderers on the Saturday before Christmas.
And Barnsley manager Neill Collins hopes the dramatic victory can be a pivotal moment in their season.
"It’s not the way we planned it,” said a relieved Collins.
"Losing an early goal is always an issue but the players responded very well, as did the crowd.
“And together we just kept going right to the very end. And you could see at the end, even with 10 men, when everyone’s up it’s very difficult and I’m so pleased for everyone that we got what I think was a deserved winning goal.
"One thing that Adam Phillips generally doesn’t lack is quality. I think he’s been outstanding, getting better and better.
"He was fantastic in training this week and if I had to pick someone who I thought would score he’d have been really high up the list."
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