KANSAS CITY, Mo. — A few weeks ago, in an office the size of a small walk-in closet in the visitors’ clubhouse at Chicago’s Guaranteed Rate Field, a reporter asked Kansas City Royals manager Ned Yost a question.



“Obviously, for Jorge Soler, health has been so important,” the reporter began. “So what have you thought of the way he’s performed?”



Yost sat back in his chair. A couple of seconds passed. Then the manager responded with a question of his own.



“Why would health be critical for him?” Yost asked.



The reporter, who stood across from Yost, took some of his own time to think. Soler had not played a full season in three years, and of course a player must play to hit home runs like Soler has, the reporter responded.



Yost took the conversation a step further.



“The reason his health has been critical for him is because it’s hampered his development,” Yost...