Today at practice, I was screwing around and started throwing this pitch that I used fastball arm action on with just a simple cut at the end. But instead of acting like a cutter, I got a pitch that had 10-12 inches of late break on it(12-6), similar to that of a splitter. The best part, is that it is indistinguishable from my fastball according to my teamates, and was only around 3-5 mph slower than my fastball.
I gripped the ball like this
but moved my thumb down on the ball so it rode the seam, making it so I gripped the outer 1/3 of the ball. I threw it hard, and used my cutter arm action(Not slider, It wasn’t a big cutting motion, just a simple 1-2 inches of supination with my hand). It was breaking late, hard, and when I started it at the hitters waistline it would bottom out and result in flailing from the batters I was facing. Anybody know what it is? Because it was NASTY!!!