It's like this:
- flera spelare är skadade = several players are currently in a state of injury
- flera spelare var skadade = several players were in a state of injury, at a previous point in time
- flera spelare skadas = several players are currently in the process of becoming injured
- flera spelare skadades = several players were at the process of becoming injured, at a previous point in time
Does that help?
So none of these seem to match exactly with the English Several players were injured — i.e. the injuries occurred at a point in the past, and the players may or may not still be in a state of injury. Would that be Flera spelare blev skadade, or something else, or is there no exact Swedish equivalent?
I noticed that we have several complaints about this being unnatural English and that "were injured" should be the only idiomatic option. However, please note that the sentence is about the state of being injured, not about the act of injuring. For instance, you might hear a pundit talk about which players are injured in regards to the upcoming match.
For contrast, "several players were injured" would be flera spelare skadades in Swedish.
In this sentence skadade is a plural, indefinite adjective, is that right? If so, why does it not end in -a? Is skadad simply irregular, or are the players "spelare" all male? Referring to the table devalanteriel posted above, I understand that the plural, both indefinite and definite form of skadad always ends in -e regardless of the gender of the plural noun it modifies, ie."all".