When training rotational athletes it is important to focus on both qualities of force production, as well as force absorption. The ability to decelerate is just as if not more important than the ability to accelerate.
Rotational patterns inherently require acceleration, deceleration, mobility, and stability throughout the entire movement. When looking specifically at the throwing/swinging deceleration pattern of baseball, you see the internal rotation of the pelvis on the femur.
If the athlete has poor internal rotation and deceleration qualities they will be subject to increased stress to the lumbar spine and further up the chain to the shoulder or elbow.
In addition to improving Hip IR, here are a couple of drills using a medicine ball to improve hip stability and better deceleration strategies.
In the first video, Felipe and I are performing a 1-leg Anti-Rotation Receive and Release drill to improve the hip stability on the lead leg that focuses on the stabilizers of the pelvis/torso. As the season goes on, we tend to lose stability and thus creates the potential for altered mechanics and injury.
The second video shows Felipe performing a Split Stance Anti-Rotation Med Ball Chop. Executing this drill properly allows the athlete to work on the deceleration of the pelvis over the femur of the front leg as well as internal/external obliques as well as adductors to absorb the force the athlete is producing.
Performing seemingly countless numbers of throws and or swings as athletes do these days, your best bet would be to prepare the body to handle the stress from the repetitive torque.