O'Grady scored the only goal of the game when he turned in a loose ball after Luke Steele had dropped Lewis Buxton's cross under a heavy challenge from Gary Madine.
The Reds did more than enough to earn at least a point from the game as Marcus Tudgay missed a hat-trick of headers, Marlon Harewood twice went close and Craig Davies was also denied.
But the pressure continues to rise on boss Keith Hill following an 11th game without a win and unsurprisingly, he turned his attention to Attwell.
"The referee gets it wrong and the ramifications of him getting that decision wrong could be catastrophic, the result has been decided by that decision," he said.
"The second half I was pleased, we had more than enough opportunities to get something out of the game.
"I just thought it was a difficult game for the referee. He will be disappointed with his performance when he comes to digest it.
"Unfortunately I don't have a second job to go to on Monday and I have to deal with it. It's happening on too many occasions that games are being decided by catastrophic refereeing decisions and we have been on the end of too many.
"I was pleased with how the players handled the occasion and I saw us strive to get something out of the game but unfortunately it didn't materialise."