Head Coach spoke to the media after this evening's clash with the Latics.
Paul Heckingbottom was left gutted after suffering defeat to Wigan Athletic at the DW Stadium.
Three goals in 12 minutes from Nick Powell helped the Latics to a 3-2 victory against the Reds, despite Adam Armstrong and Ryan Kent helping the Reds to a 2-0 lead.
Hecky felt the Reds were made to pay the heaviest possible price for not defending as stoutly as they could as the hosts escaped with all three points.
He said: "All our hard work to get to 2-0, we were defending well and they had lots of shots from distance and we weren't really troubled, we were a constant threat on the counter. After the second goal, we started to control the ball a lot better and it was a crazy five minutes.
"We focus on us and our players and mistakes are mistakes. You have to limit them if you want to play as high as you can and we know that. The worst things are the fundamentals which we don't have in a Barnsley team which we saw and it's cost us the game, and the players concerned know about it."
Individual errors were somewhat to play for the Reds' defeat, Hecky added that those concerned realised afterwards the impact that they had on the game.
"They know exactly what they've done wrong and if that happens they don't play. It doesn't matter when it happens we don't do it and the players wonder why I go mad about certain things and when it costs them the game, they realise and I hope that's the case and that's what we have to take from the game.
"We can't take the points but that's why we don't do those things. We do certain things and when you don't, it can cost you," he added.
Despite the result, Hecky was pleased that Armstrong and Kent weighed in with a goal apiece, but added their contributions ultimately counted for nothing following a mad few minutes.
"Kenty did well, he was a threat throughout. I spoke to him at half time about decision making on the counter and he did that better as well second half. He's created one and scored a good one and I thought him and a few others had good games but it counts for nothing.
"We win as a team, we lose as a team but things we don't do were evident today and things we should always do weren't evident at certain times and that's what has cost us, that wasn't what we're about." he added.
The Reds are back in action on Easter Monday against Brentford at Oakwell. You can buy your tickets HERE for as little as £10 for Adults and £5 for concessions! #OnceARed