You can reduce the risk of your players suffering an injury, but you will never be able to completely avoid them. Here are some examples for things that you can do in order to lower the risk of an injury:
1. Develop your stadium facilities
2. Avoid too much training and too many Friendly Matches (arranged by you)
3. Avoid your players having a too aggressive Tackling Style
4. Do not use Marking Style Settings
Please bear in mind, however, that at the end of the day injuries are part of any football match and, as in real life, recently injured players may suffer a relapse if you don’t give them time to recover.