When Voros McCracken wrote his seminal piece on pitching and defense 11 years ago, he helped change the way people — fans, writers, even general managers — think about run prevention in baseball. Where once we used to throw most of the blame for a hit on the pitcher who gave it up, McCracken helped us realize that a slew of other factors go into whether a ball hit into play falls for a hit. For many people in the game and others who simply watch it, our ability to recognize the influence of defense, park effects, and dumb luck can be traced back to that one little article.
Today, we have multiple stats that can help us better understand a pitcher's influence on the game. Fair Run Average (FRA), Fielding Independent Pitching (FIP), and Expected Fielding Independent Pitching (xFIP) all attempt to parse the events a pitcher best controls from those over which he has the least control. The fantasy implications seem obvious. If a pitcher, say, posts a much higher ERA than xFIP for a few weeks or a few months, we might expect luck to start working in his favor in the future, and for his ERA (and other fantasy stats) to start improving. If he puts up a much lower ERA than xFIP, you could argue that his good fortune might be due to run out soon.