Are you sure you had 9 injuries at the same time? Because according to the game info, the maximum number of injuries a team can have at any one time, is 7.
i got screenshot of 8 injured players in the old forum.
for past few seasons, i'm getting just about 15 injuries in a season. previously, i would get around 25-30 injuries per season. don't know if it has something to do with improving the facilities.