Yeah, my guess is that players have an embedded injury rate some higher some lower. If every action has a small chance of injury then those most involved will be more susceptible. I have an AMR/AMC that has just picked up his 6th injury in matches (see below).

Can't really comment on Training but I think Frequency of Training will have a greater impact than any player factor.

(Although I must admit I trained an alt team player obsessively using 80 packs just to see what happened - in second 'train' he got injured, I healed him and then all those packs later no more injury.)

In the last 3 days I've had 3 injuries in matches - 3 days my longest serving player, 18 days my left winger and 4 days my right winger. They are important players but 12 out of my 15 active players would be considered important - so not sure I can draw much from that.