Monahan also might have higher than normal pain threshold, so even though he's injured he doesn't feel that bad. Good training staff can make a huge difference there.
Personal experience: I hurt my knee while running some 10 years ago. Went to see doctors once a week for 4 weeks I think until they sent me to MRI, and it turned out there was a stress fracture. The doctor then told me that usually one doesn't get this bad stress fractures from just running. Well no shit, I walked with for 4 weeks because nobody realized what was wrong, of course it got worse in that time.