That's an interesting point re. practice matches, I hadn't thought about that.
Looking at my 3 season's injury causes, the relative number of injuries does seem roughly proportional to the condition loss incurred in the actvity* - I generally give all my squad 1 of each type of training per day, assuming they also play a match. And I try to use friendly matches to ensure I play 2 matches per day (I failed on a few occasions while on holiday the last 10 days of last season and did extra training instead for the reserves), so the number of cup+CL+friendly matches will be roughly equal to the number of league matches**.
*Warning, 50 injuries is still a very very small sample
** 14 injuries in 79 league matches means you expect to get 1 every 5-6 league matches). Unfotrunately I haven't kept an exact count of the number of Cup/CL/Friendly matches played over the seasons. Based on my History I'd say that (over the last 3 and a bit seasons) I'd have played:
Cup - 22 matches
CL - 39 matches (almost identical chance of an injury as in league matches)
Friendly - about 30 (so slightly higher injury probability but balanced by low Cup injury rate - possibly a small-sample issue. Though the severity of injuries is lower as a balancer).