"You're just getting more and more realistic views of what opposing pitchers have," catcher Riley Adams said of the Nationals' new Trajekt Arc machine. Sam Navarro / Imagn Images WEST PALM BEACH, Fla.

The pitcher steps onto the mound, and the game slows, just for a moment. Cleats press into the dirt. Fingers find familiar seams. There is a brief pocket of quiet where years of training, repetition ...