Has Corbin ever tried to develop a third pitch? A second offspeed pitch could be very effective. Batters recognize offspeed, and if you only have one offspeed pitch, a slider, the batter knows it's a slider. If he had a curve, he might recognize it's offspeed but not be able to distinguish slider from curve. A changeup would be even more effective (since it's often the same speed as a slider, where a curve is much slower). But a changeup seems much harder to develop.
He has tried the change up. I see different things on different sites but this one shows he is not throwing a two seamer either. Another site shows he throw a two seamer but no different speed wise from his four seamer. That’s a problem also.
https://www.pitcherlist.com/player/patrick-corbin/
