Answer:
One way a person can sustain an intentional injury is if the dive in football (soccer), for example. In the process of diving, the player will typically fake being taken out, and in the process, they will over exaggerate the challenge against them. In this process, they will make the challenge look much worse than it actually was. However, due to this over-exaggeration, it’s possible that the player might actually injure themselves, whether it be due to contact they make with the ground, or pulling a muscle/stretching a muscle too far.
One way a person can sustain an unintentional injury would be if the defender made a questionable tackle in an attempt to win the ball back. Sometimes, a defender will slide tackle in an attempt to reach for the ball, however, it can be difficult getting the timing and the angle right in order to get the ball without fouling the player, let alone without touching the player. As a result, when a defender attempts to slide to get the ball whilst being located behind the attacker, it's often that the attacker gets tripped up in the process. This could lead to the attacker getting injured unintentionally, but injured nonetheless.