I'm not going to let a wonky shoulder keep me off the tennis court. The rotator cuff injury from falling on the ice at Berkeley Iceland isn't healed yet, and I'm sitting out this season of the local tennis league to rest it.
But where there's a will, there's a way. I've started practicing left-handed, and now can do everything OK that way except serve. Strangely, I had an easy time learning to judge topspin backhands on the left side, where I sometimes mishit the ball doing that with the right arm. Not sure if that's a vision thing, or a holdover from a right shoulder injury from the teenage years.
The rotator cuff is supposed to take "in the low months" to recover from this type of injury. As with ribs, the doctors don't do a whole heck of a lot unless there's something really serious. If it doesn't come all the way back, then an MRI is the only way to see exactly what's wrong. There are various tendons and ligaments that fall under the heading of "rotator cuff", plus the labrum which has its own set of things that can go wrong.