You only get one mistake?
Firstly, I don't think it was a mistake.
Secondly, if anyone in any job or team could make one mistake they would be scared to make them. You need to make mistakes to learn from. That's how you get good!
One of many things I like about McD is that I believe he IS learning and will get better. Some other coaches don't have those abilities. I think it is a positive. He does the work, studying, self reflection and tries to learn and get better.