I don't want to engage in an argument with you as I'm not an expert in this field. However, what I do know and what history has review is that certain injury can linger longer than you expect, sometimes never healing itself at all. Groin type injuries certainly falls into that category for mine, and there has been countless examples of how such an injury can linger/reoccur during the course of a season. The healing process is not as simple as just resting, regardless of how long the duration of that rest.
I'm not about wishing ill upon J Kelly, but simply just to point out the basis for my comment. Every player has an injury risk attached to them, some are new and unexpected whilst some are borne through history. The fact that J Kelly has that recent history makes him a higher risk in my opinion. I'm all for coaches taking risk versus reward type of selections, I started with a few 'risky' players myself so am not immune to it, as long as they're fully aware of the risks which they're buying into. To that end, I find your statement 'always take a player without any injury concerns' a little misleading.