It was McFadden's first miss in five attempts for Blues.
McFadden admitted: "It was a poor penalty. I don't know why, but I changed my mind where I was going to put it. But I will be ready to take the next one."
Roger Johnson said McFadden was not held to account by his team-mates.
"He was disappointed," he said. "It was a penalty, he's not meant to miss.
"You never know. Had it gone in, they may have ended up scoring as well.
"His head's up and we will just crack on with the next game now."