I'm almost 100% certain that I have a rotator cuff injury in my left shoulder (I'm a lefty) caused by all of the tennis I play. I play about 5 times a week for my high school team and have a big serve. Lately, my serve has been off and I'm slicing the ball way too much, and I don't mean to be. It's put a lot of strain on my shoulder. The movement and flexibility is noticably different than that of my right shoulder. I wouldn't call it painful, but I would say that I can feel a hinderance. My question is, will rotator cuff exercises make my already injured cuff worse, or will it improve it? Also, I have no intention of quitting tennis at this point because my high school team is in the state tourney (we're going all the way, btw ) and I realize this will only make it worse. I of course will tone down my serve (maybe even serve underhand), but is it ok to still hit my groundstrokes with authority? How damaging would that be?