This gets back to one of my all-time favorite sports cliches - the "successful" surgery.
99.9% of the time an athlete has surgery, the team tweets or puts out a release stating that the surgery was "successful."
Well, like it or not, medicine is not an exact science. doctors and patients are human beings, not robots. I know a guy who messed up his foot in a work-related accident and he has now had three surgeries on it over 2 years, and it still isn't 100% right. I know another guy who had knee replacement, and something went wrong, so he hobbled around for a while and wound up having another replacement surgery.
just because most surgeries are successful, that does not mean that all surgeries are successful. I get that Zim isn't happy, but I assume the Vikes gave Darrisaw a medical screening before they drafted him. if Zim wants to rip someone, rip whoever cleared Darrisaw and told the Vikes he was good to go.