You Should Trust the Projections
Here on FanGraphs, a lot of the data we present is built around future projections. We host both pre-season and in-season forecasts from multiple systems, and these forecasts form the basis for many of our tools, including our Playoff Odds model. It’s safe to say that we like forecasts.
But I know not everyone reading this post trusts the projection systems, especially when they are forecasting things that we don’t want to be true. It’s natural to want to discard prior information when it doesn’t align with what we want to believe, and often, the forecasts serve as a wet blanket alternative to enthusiasm and excitement. What’s to like about a system that takes the fun out of breakout performances, or tells us that we need to be more patient with the guy who just looks terrible every time we watch him?
And it’s not like projection systems are infallible. Those forecasts never saw Cliff Lee coming, and they certainly didn’t anticipate Jose Bautista was going to go from career scrub to superstar at the age of 29. There are plenty of examples where players made dramatic, unexpected turns in their career arc, and using their track record to project their future would have been wrong. The fact that there are players who have radically changed their performance base allows us to extrapolate that possibility to every player who is performing in a way inconsistent with their projection.
But we just shouldn’t do it. Projections might be fun-sucking, soulless algorithms that are incapable of picking up on adjustments that players can and do make, but the reality is that these forecasts do a pretty good job of predicting the future, even for players whose current performances and projections don’t line up at all.



