There's a few general categories of injuries: roughly speaking, the ones that happen during play, the ones that happen on the practice pitch, and the ones that come out of the blue and you can't do much about (like player gets sick).
In addition to what's mentioned in other comments, if your players are tired a lot, they'll pick up more injuries. In L1 you probably don't have a huge squad nor a big staff, but do look at whether they're being pushed too hard in training and whether you can in general improve your training environment, this has the possibility of leaving your players more fresh for when match time comes around.
Some players are also more injury prone than others. That's a hidden attribute, but you can maybe draw some conclusions looking at a player's past injury history.
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