Let’s say that the striker is closing in to the goal post on the right side. As a defender, I am running towards the middle of the right post and the striker. I perform a slide tackle towards the line in anticipation of a shot from the striker.
Firstly, it would be rare for such a tackle to be performed; it’s bad for a defender to commit themselves like that. Especially at a higher level, oppenents will be able to read your actions and trivially side-step your tackle; they’re then through on goal, and you won’t be able to support your defence in time.
Providing I’m reading your scenario right, then it shouldn’t be judged as a foul. You’ll get the ball first, it isn’t a tackle from behind; so, providing it was otherwise a legitimate slide (feet weren’t high, studs weren’t showing, it wasn’t a lunge, you don’t go through the player), I can’t see the referee giving a foul for it.
As for the striker getting injured; I doubt it. It won’t catch the striker by suprise per-sec, but just late enough so they can’t navigate themselves out of the situation with the ball. They’ll still see the tackle arriving, and will be able to catch themselves with their arms, roll off the tackle, or even step/ jump over you.