I have had sprains before so I know what they are. You can sometimes get a sprain from getting hit, but impact wasn't the best word to use. I should hasve said "acute". Sprains are usually acute as opposed to something chronic. So, a sprain might cause some damage that is not directly related to pitching and it might heal. A strain sounds like something that is caused by the repetitive motion of pitching. Either way, it's not good news.