Haye has pulled out of so many fights for DODGING reasons with fake injuries (once vs. Vitali, once vs. Wlad) that when he had actual legit injuries he couldn't pull out anymore, especially not with PPV money on the table.
He didn't even mention it, let alone use it as an 'excuse'. Although as far as excuses go, I'd suggest it's a pretty good one.
I think you should be at your best, if you're injured, pull out. Though I understand it's not always that simple.
Because people bet on fights I think they should pull out if not 100%. I know they may miss out on a pay day or think they can win at 85% but they should reschedule if possible or not go through with the fight IMO.