When one considers that just about every pitch is a "feel" pitch, it's essential that the pitcher learns to get a true sense of the ball, and if s/he should lose that sense of the ball there can be big trouble. Phil Rosengren once discussed the concept of getting the feel of a pitch, of making it an extension of the hand and arm and thus getting the true sense of one's pitches---if you can find it, there's a four-minute video demonstrating this.
I remember one time when I was watching Eddie Lopat, my wise and wonderful pitching coach, conduct a workshop for a bunch of high-school pitchers, and he was dealing with a junior, about 17, who had suddenly lost the feel for his curveball and couldn't seem to get it back. Steady Eddie demonstrated an approach to the problem that did the trick. He told the unhappy pitcher to get off the mound, sit down on a bench and pick up a baseball. He said, "Feel it. Feel all 108 seams on the ball. Feel the smooth surface of the ball. Get the entire sense of the ball...let it talk to you." He had the kid on successive days get up on the mound, but not to throw, just to repeat what he had done the first day. Then, the next day, go into the bullpen, get up on the mound, repeat the same procedure---and then just stand there with the ball in his hand and think about what it would be like to throw a good curveball---really get the sense of it. Then, he was to get a catcher and throw ten pitches, always being aware of the ball, what it felt like, and what it would feel like to throw a good curve. Ten pitches, then fifteen---always being aware of what it would feel like to throw a good curve. The kid got the feel for his curveball back and had no further trouble. A simple exercise---and it worked. 8)