I understand where you are coming from, but I also think you are taking things a little too extreme. Or are you saying that Darren was the only reason you ever watched a stream, and didn't bother to watch anyone else?
Everyone makes mistakes. What makes a man is what they do when they do make a mistake. Did Darren make a bunch of excuses to why he was late? NO! He owned up to it and apologized to everyone! That is the kind of character you are looking for in someone to back or bet on!
Will he miscue or miss a ball at some crucial point in a match? Sure he will, he is human. I see no difference here with the sleep in. It's a fluke that happened. And, with his character, you can now safely say that it is extremely unlikely that it will happen to him again! That means one thing, you no longer have to worry about that mistake ever happening again with him.
Too bad for you that it was your money on him when he made the mistake, but now you can rest assured that it won't happen again with him. In my thinking, now is the time to put money on him. He will be more attentive than he was before.
You talk of professionalism. Nobody gives 100% 100% of the time. Not in any job. But, when it becomes too mundane, things slip and their is usually a cost to it. The real professionals are the ones that then immediately get that 100% back and that is the time to be in their corner.