There are 2 types of injury:

1. Light injuries - these are shown with an orange image and mean that the player will play any matches with reduced physical attributes

2. Heavy injuries - these are shown by a red image and cause the player to be unable to play in matches. A substitute will be put into the team in his place. Of course if all the substitutes are injures as well then he might have to still play...but he'll be useless!