FORT MYERS, Fla.—It’s no secret that baseball’s grip on the collective imagination of the country has slipped. Football is the national sport now. Basketball is king with the social-media generation. Though America’s pastime isn’t dying, the long-term trend lines are worrisome.

But against all odds, there is a player in the Upper Midwest who is capable of healing what ails the game. His name is Willians Astudillo, and he is here to save baseball.

Astudillo...