People who like baseball call it "the thinking person’s game," but for the first 100 years, baseball was governed by a surprisingly limited range of critical thinking. Decisions were made by insiders, the current and former players who spent a lifetime around the diamond, and did things mostly one way: the way they've always been done. But in the last 3 or 4 years, that storehouse of common knowledge—much of which was kept guarded in a true "old boy's club"—has been cracked wide open. Now the game isn't driven by intuition, it's driven by data. And the math nerds who rode the bench in Little League—if they played at all—are now telling pro ballplayers what to do. Journalist Travis Sawchik tells Steve Paulson the story.