I had an injury-ridden season just recently. I attribute it more to teams doing ONLY hard tackling against my side, at least, thats what I think is happening!
Broken legs, broken feet, knee tendonitis, it was a nightmare. But the season still went very well, as the squad is deep, and although it was the veterans (and first choice) that got injured the up-and-coming youngsters were good enough for first team playing time.
Now when I have a game like that, and notice the ref isn't doing much in the way of giving the opposition cards I switch my teams tackling to Hard as well! And target their low condition players! Back at ya, AI!