Subject: Slight Injury

What effect does that have when playing in a match?

From my experience, a drop in performance of about 25%, and if they get injured quite a lengthy injury!

I suspect the drop in performance is linked to how badly injured they still are.
So a guy who only just became slightly from +8 will be worse than someone who will be better tomorrow

You suspect correctly.

Yeah that makes sense, i would expect the sub-levels to be "daily"