This week at BP Boston I have an article examining differences between the three major publicly available baseball projection systems: Steamer, ZiPS, and PECOTA. Specifically, I looked at where they differ in their expectations for Red Sox players. The three systems are based on similar algorithms, but they make different assumptions and rely on different metrics in a couple of key areas (e.g., defense, pitching). As a result of this the final projections for a given player can vary substantially. I gathered the projections from each system for each of the likely Red Sox regulars and then focused on the players for whom the systems’ projections differed by at least one win above replacement. It turns out that, as I suspected, defensive metrics and the way pitchers are evaluated drives most of the differences between systems.

Click over to BP Boston to get more details: Pick Your Projection: 2017 Red Sox Edition