What does Horton's contact being uninsured mean?
It means that they owe every cent on it. If it was insured, then they would only pay the insurance and the insurance company would pay the rest. Horton isn't going to play again, so Columbus would have to pay his entire salary for him to do nothing. Clarkson is a body - he's a terrible body in Toronto, but at least he will play and can possibly make positive contributions on the ice. Maybe he won't, but it beats paying Horton to do nothing.