The morale ( in answer on craciot) has not directly affect on injuries, but indirect it can be.
Let me explain:
When your squad has low morale, they perform not at their best. In other words, their play can be more 'dirty' than with a perfect morale.

But what about injuries:
When your squad has a low morale, and their game isn't the best, you'll have an increased change for getting injuries. Also it counts when your opponent set their tactics in a way that you haven't much possession, what will result in that your squad has to work 'harder'to gain any chances at all.....
With that in mind, and knowing that their morale has dropped, your squad will have to much trouble to play the match 'normally'.....with many injuries as result.

Noticed: this is only a personal opinion, if you have to formulate or calculate an answer for that many injured players.

Don't know if this all is true, but there must be some sense behind conditions and morale.


Of course you'll never know for sure what your opponents tactics are...also you'll never know for sure why you have one day 5 injured players, and the next month none.....
Game-engine calculates, and we all must have just a little bit luck on our side!