It's more bad luck than anything. Look at Kris Jenkins.... same knee two years in a row, third time in his career. I'm sure Bob Sanders puts in work in the off-season. That being said, I'll pass on this guy.
It's amazing that a strong safety is the difference between the Colts run defense being good and way below average.
Yeah all of those injuries don't put mileage on his body. Give up this dream of yours. It's kinda sad.