Once again: why do you want to tell a story about failure, a story with an unhappy ending? About a man who through no fault of his own loses his job? (It wasn't his fault that he needed surgery, was it?) What's your dramatic point (other than life is brutish, short and unfair)?
And further: he may be in denial about the severity of his injury. But isn't it also the case that if he weren't in denial, if he didn't believe he should return to work, he will be fired for not showing up?
So if he thinks he's well enough to return to work, he's going to lose his job when he does. And if he doesn't think he's well enough to go, he's going to lose his job when he doesn't.
So, he's damned if he does, damned if he doesn't. No matter what he does, he's going to be fired. Right?
Ergo the alleged "character flaw" seems irrelevant to the outcome of the man's struggle. With or without "the character flaw", he's fired, doomed, f###ed!
But in drama a character flaw is not irrelevant to the outcome, it's germane, it's pivotal to the outcome of a character's story. If a character lacks the flaw, then there would be a different outcome.
But, to repeat, the outcome of this story seems to be independent of his "character flaw". No matter what he does, he loses his job. Which means it doesn't seem to be a character flaw germane to the plot.
All that his "character flaw" seems to determine is the circumstances -- HOW he's fired, not WHETHER he's fired. But shouldn't a character flaw determine WHETHER as well as HOW?