In the previous drill (three degrees of complexity), the feeder used alternating placement to increase the difficulty of the drill. In this drill, the feeder now uses random placement, and also forces the trainee to decide whether to use a different stroke, increasing the complexity to 4 degrees.
The feeder will now block the ball to the trainee's backhand corner most of the time, but every so often (typically once every 1-5 strokes), the feeder will block the ball to the playing elbow of the trainee, forcing him to decide whether he should play a backhand or forehand, and making the trainee move in order to play the ball with good form.
Common variations to this routine include the feeder counterhitting the ball instead of blocking, or the trainee driving the ball instead of looping.
Degree of Complexity
This is a four degrees of complexity drill, since the placement of the ball changes on a random basis to a fixed second location. The trainee has to decide whether to use a different stroke (forehand instead of backhand), and the trainee has to use his footwork to hit the ball with good form.
Purpose of the Drill
This drill is another variation of the backhand drill, used from time to time to make sure that the trainee is recovering to a neutral position, from which he can hit a forehand or backhand. If the trainee is recovering favoring his backhand side, he will struggle to hit the correct forehand stroke in time, and will tend to move across to the center of the table to hit a backhand instead.
By introducing a random element into the routine, the trainee does not know when the ball placement will change, and must remain alert in order to move and play a successful stroke.
Thus the trainee is practicing his backhand stroke, his forehand stroke, his recovery to a neutral position, his footwork, and his anticipation.
Benefits for the feeder include practicing his forehand block or counterhit, and aiming at hitting the playing elbow of his opponent when desired.