Excerpt from Complete Conditioning for Baseball, published by Human Kinetics
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" This is always a red alert area for baseball players and coaches.  The shoulder all together is a large very powerful muscle group.  The shoulder assists in almost all upper body movements.

" The deltoid and rhomboid areas which make up the bulk of the shoulder area are powerful, thick, muscular dense muscles. However very seldom are these muscles injured in baseball. It's always the smaller muscle groups known as the rotator cuff area that get most of the  injuries. Neglecting these small muscle groups would be detrimental to a baseball player. 

" Common imbalances to front deltoid and neglect to these small muscles is one of the major reasons for chronic and acute arm problems. 

" These muscles are not isolated through conventional shoulder exercises. To maximize conditioning of this area specific exercises with light weights and tubing must be used. "

• External Rotation at 0 Degree Abduction - Standing with involved elbow flexed at side, elbow at 90 degrees and involved arm across front of body. Grip tubing handle while the other end of tubing is fixed. Pull out with arm, keeping elbow at side. Return tubing slowly and controlled.
• Internal Rotation at 0 Degree Abduction - Standing with elbow at side fixed at 90 degrees and shoulder rotated out. Grip tubing handle while other end of tubing is fixed.  Pull arm across body keeping  elbow at side.  Return tubing slowly and controlled.
• External Rotation at 90 Degree Abduction (Slow) - Stand with shoulder abducted 90 degrees and elbow flexed 90 degrees. Grip tubing handle while the other end is fixed straight ahead. Keeping shoulder abducted, rotate shoulder back keeping elbow at 90 degrees. Return tubing and hand to start position slowly and controlled.
• Internal Rotation at 90 Degree Abduction (Slow) - Stand with shoulder abducted to 90 degrees, externally rotated 90 degrees, and elbow flexed 90 degrees. Grip tubing handle with other end of tubingfixed straight behind. Keeping shoulder abducted, rotate shoulder forward, keeping elbow at 90 degrees. Return tubing and hand to start position slowlyand controlled.
• Diagonal Pattern (D1) Flexion - Gripping tubing handle in hand of involved arm, begin with arm out from side 45 degrees and palm facing backward.  After turning palm forward, proceed to flex elbow and bring arm up and over uninvolved shoulder.  Turn palm down and reverse to take arm to starting position.  Exercise should be performed in controlled manner.
• Diagonal Pattern (D2) Flexion - Involved hand will grip tubing handle across body and against thigh of opposite side leg. Starting with palm down, rotate palm up to begin. Proceed to flex elbow and bring arm up and over involved shoulder with palm facing inward. Turn palm down and reverse to take arm to starting position. Exercise should be performed in a controlled manner.
• Diagonal Pattern (D2) Extension - Involved hand will grip tubing handle overhead and out to the side. Pull tubing down and across your body to the opposite side of leg.  During the motion lead with your thumb.