My overall injury stats updated to end of last season:
13 injuries, totalling 56 player-days (before healing). 152 packs used (thank goodness for farming packs via videos on iPad in the UK)
As mentioned above, 15.3 injuries per season on average, and 65.7 initial days out. And in most normal seasons I'd expect less than 20 injuries and less than 85 days out.
Broadly there's a just-under 1 in 5 (18.6%) chance that I'll have a player injured in any given match, and a 1 in 20 (5% - though it varies proportionally to the stamina loss involved in each type of training) chance I'll lose a player in training. That equates to an injury every 1.8 days on average (I did go a whole 8 days between injuries in the middle of last season though!)
And the 2 most common types of injury are (thank goodness) lower down the severity scale - over 1/3 of all injuries are either ankle strains or grade1 hamstring.
Note, I play a full 22-man squad, rotating players so that generally they all play 1 match, and have 1 of each type of training per day. I never start a player with <90% stamina, and never train a player with <80%. And my medical facilities and pitch are maxed out. I also have a fairly young squad (ave. age ~21), and I train my players so that their physical fitness matches their dominant discipine (attack/defence)