More information would be helpful to find a reason for your injuries. For instance, are these injuries sustained on the training pitch, or during a game?
Giving players a rest between games (a day off training) can help them recover quicker and so be less likely to pick up an injury. Substituting players with low conditioning during a game will also reduce their chance of injury. What kind of tactic do you play? Possession-based tactics generally invite more tackles on your players which result in more injuries.
Alternatively, signing players with high natural fitness and stamina may help with this problem, as well as improving training facilities, and hiring better fitness coaches/physios. Hope this helps!