There’s a problem in “fixing” a pitcher’s mechanics. In making them safer, you might make them ineffective. Chris O’Leary, a pitching “expert”, has taken a look at Francisco Liriano and the changes he’s made.
I say “expert” not out of disrespect for O’Leary or his work, but because no one that looks at pitching knows what they’re seeing. At best, we can speak in generalities, rules of thumb, and conjecture. Yes, I’ve done it and will do it again, but none of us have the knowledge needed. Of course, neither do the teams in most cases. I know of only three teams that do everything from baseline MRIs, in-season objective monitoring, and motion analysis that allows us to get to the really important information - joint loads.
Without that information, the best we can do is discuss, not educate. If there’s any lesson from Pitch FX, it’s that we should be using our lying eyes as a secondary source, not the primary.
Moreover, I’m going to quibble with O’Leary’s assertion that the slider is a harder pitch on the elbow. Studies have shown that, thrown properly, the “cost” of a slider is not significantly higher than a fastball. (You can check for yourself at this link. I’m sure you’ll recognize a couple of the names involved, attesting to the quality of the study.) The big caveat is “thrown properly,” which allows any pitch to turn into a potential injury, not to mention anything of in-game or seasonal fatigue issues.
There’s more we don’t know about pitching than we do. As we get more and more people discussing it and using advanced tools and video, just keep that in mind. Even when it’s me.