Experience has taught me that many hitters fail to execute the Turn Phase when swinging at full speed. There is a hurry to get the barrel around to the ball, causing the hitter to lead with the upper body and bring the hips around afterward, a flaw I call "hips trailing". Be sure to execute phase 2 properly when swinging, and lead with the hip turn.
2.1 SHIFT WEIGHT, ELBOW TO HIP
The first movement of the swing is a shifting of the weight forward toward the ball. It's important to shift most of your weight (70-80%) onto the front foot to enable your back hip to turn freely. As you shift your weight toward the ball, the front heel will drop flat and the back heel should start to lift. At the same time, bring the back elbow down toward the back hip pocket. This is the last point in the swing where you can hold up; once the hips start to turn, it's difficult to stop the bat:
2.2 TURN THE HIPS
Once you have shifted weight onto the front foot:
Phase 2. The Turn
The second phase of the swing is the Turn, and it is the first phase of the swing proper. The starting position for the Turn phase is position 1.3, the Ready-to-Hit position, which the hitter attains at the end of the Pre-Swing. The hitter then shifts his weight forward toward the ball, brings the back elbow toward the hip pocket, and turns the hips.
The Turn is the rotational phase of the swing and involves a rotation of the lower body. The upper body and arms stay relatively quiet and do not rotate much during this phase. In the next phase (Phase 3), the hitter will release the upper body and arms.