Moving along from running. My son (2016) pitches infrequently (usually catches or plays corners) so he doesn't work on his pitching daily. He finds that unless he works on pitching frequently he looses command of his curve ball. No problem with the 4 seam and 2 seam fastball, or change ups, just the curve. Do you have a suggestion on another breaking pitch to learn that might be easier to retain than the curve ball?