third coast.. said:
You know what I meant
I don't know what's so hard to believe. Sometimes you don't even realize what you're not doing correctly. You get in a groove (or in a rut).
Looking at the ball with both eyes helps with depth perception and spin recognition. But you can very easily drift to one eye without realizing it. If you ever read moneyball, the story of chad Bradford that isn't explained in the movie was that he didn't even realize he was throwing truly submarine. And didn't realize how much further down he kept going until he scraped his knuckles on dirt delivering a pitch. He had consciously lowered his mechanics to sidearm, but kept going lower as it improved results without realizing he was.
The eyes piece is just a mechanics issue in Yuli's swing that broke down. It's fixed now and you see the results. Anything on the inside-middle portion of the plate gets tattooed. He's recognizing his pitch and starting his swing earlier due to that recognition and can get to that pitch, especially up in the zone. It's more complex than "keep your eyes on the ball".