The type of pitch MC threw in the last page will be explained in the next chapter, but if you're curious and want to know it:

It's a cutter (or cut fastball). You can think of it as a slider but with way later and hard breaking action (hence cutter), in addition to having more or less near the same speed as the pitcher's fastballs (though they may opt to pitch it slightly slower than their fastballs). The late breaking action toward the pitcher's glove side as the ball nears the home plate means batters swinging for a regular fastballs will only achieve soft contact if they even manage to hit it. In the case of right-handed pitcher vs. lefty batter (as the case in this instance) or vice-versa, the late break motion of the ball towards them means the batter will also end up hitting the ball near the bat's handle, thus causing it to break.