The Tractor Boys took a 4-1 advantage into half time at Pride Park, but the home side rallied after the restart to earn a 4-4 draw.
"We conceded some bad goals - goals that we wouldn't normally concede," he told reporters. "I was a bit annoyed at how we gave them a chance just before half-time. I was livid at that because that sent them in feeling a lot better at half-time.
"It changes because they've got little or nothing to lose after being overrun in the first half. They had to change something and they did. They got Will Hughes further forward and made a better fist of it. I'm not happy about it, but I'm realistic enough to know that it happens sometimes."
The result has left McCarthy's team 10th in the Championship standings.