Fielder had a degenerative spine. He was also morbidly obese. It's entirely possible for these things to exist simultaneously and not be directly related to each other. This would be like blaming Vlad's history of wrist issues on the fact that he's a heavyset player instead of being someone that swings a bat hundreds if not thousands of times a week for a living. Prince played a highly rotational sport and had a rather violent swing, both of which are things that would have greatly exacerbated a degenerative spinal condition.