I have a theory...

The players that you put arrows on get injured more often than others, possibly because they exert much more effort in matches i.e they run up & down more than other players without arrows.

I have noticed that for my team, my defenders rarely, and I mean very rarely gets injured. I don't play arrows on them. And when they do get injured it is normally during training.

Both my AMR & AML gets injured almost twice a season because I frequently use arrows on them.

This is not concrete but it is just a theory. I believe you shd prepare yourself for more injuries when u have more players with arrows on.