GLENDALE, Ariz. — Tucked inside a staggeringly beige business park seven miles up the freeway from the Dodgers’ spring training stadium, sits a cavernous batting-cage complex and baseball-coaching center known as D-Bat Peoria. Yasmani Grandal spends much of his winters there.



One day last November, the Dodgers catcher said he was taking his standard swings when he noticed a young coach drilling two college players. The exercises resembled videos Grandal had seen on YouTube. He thought they might have something to do with launch angle, the subject that has shot from unknown to ubiquitous within major league clubhouses in recent seasons.



Initially, Grandal stood “very against it,” he said. Slowly, he opened to the idea, aided by the internet and success stories of the likes of Josh Donaldson and J.D. Martinez. That day, what he saw and overheard intrigued him even more.



“So,” Grandal said, “I started asking...