THE BAT Projection System Joins FanGraphs!

What’s up, FanGraphs!  My name is Derek Carty.  If you’ve been into sabermetrics long enough, perhaps you recognize me from my time managing the fantasy sections for Baseball Prospectus and The Hardball Times a while back.  The past half-decade or so I’ve been focused solely on daily fantasy sports, most notably with, Baseball Tonight, RotoGrinders, and on Twitter (@DerekCarty).  I’m so pumped to be announcing today that I’m getting back involved publicly on the sabermetric side (privately, I never left!) by integrating my projection system, THE BAT, into the offerings here at FanGraphs!

If you’re into DFS, you may have heard of THE BAT.  I’ve been building this system for the past eight years, and 2018 will be the fifth season it’s been available publicly, first at Fantasy Insiders and now at RotoGrinders.

So what is THE BAT, exactly?  In simplest terms, it’s a projection system in the same vein as Steamer or ZiPS.  Given my sabermetric pedigree, the backbone of the system has all the usual components: regression to the mean, multiple weighted seasons, aging curves, and minor league equivalencies.  But it also has some very cool and unique elements.

Up until this point, THE BAT has strictly been for DFS purposes – projecting outcomes for individual games based on basic factors like hitter and pitcher and park quality but also on things that are very day-specific:

  • Umpires
  • Specific defensive alignments (Braves decide to play Freddie Freeman at third base all of a sudden? That’s accounted for),
  • Weather factors (Temperature, sure, but also more granular things like humidity, air pressure, and special wind factors for the anomalous Wrigley Field)
  • Platoon splits (Regressed, of course, using methods from The Book while also accounting for things like pitcher arm angle and pitch mix)
  • And a bunch more

Player stats are backwards-adjusted to account for all of the individual circumstances they’ve faced in the past in order to gain a truer estimate of a player’s underlying talent level.  On the season-level, that underlying talent is then forward-adjusted based on the circumstances the player will face for the remainder of the season.  Which parks he’ll be playing in, what the weather is like in those parks at the time of year the games will take place, the quality of the opposing hitting/pitching on the schedule, etc.  While I can’t give away all of the proprietary factors that feed THE BAT, a few more of the cooler ones I can divulge include:

  • Pitcher role adjustments (A pitcher like Danny Salazar, who projects for innings as both a starter and a reliever, will project for different stats in each role)
  • Dynamic park factors (The humidor in Chase? Accounted for.  The Angels lowering their right field wall by 10 feet?  Accounted for.)
  • Position-based age curves (Catchers age differently than first basemen, after all)
  • Exit velocity

This has led to great success for users in their DFS contests, and accuracy testing of the system has been quite good.  Internal tests against other DFS systems show it to be elite, and published tests of THE BAT’s daily team and game projections consistently outperform Vegas lines, which many DFS players consider to be the pinnacle of forecasting sharpness.

Given this success, I’ve gotten a ton of requests from users who want a season-long version of THE BAT.  After building out the functionality for it, I couldn’t think of a better place for this version of the product than here at FanGraphs.  Not only would it be freely available as a sort of “thank you” to these users for their support over the years, but FanGraphs is also easily the go-to place for statistics, in my opinion, and it’s my hope that the addition of THE BAT proves valuable for everyone who uses it.

If you like the sound of THE BAT, check it out here at FanGraphs on the player pages, on its own sortable leaderboard pages, and in the fantasy Auction Calculator.  If you find you enjoy it, I hope you’ll also consider trying out the DFS version at RotoGrinders, available for pre-sale now!

If you have any questions about THE BAT or really anything baseball-related, please feel free to drop a comment here or tweet at me (@DerekCarty).  I’ll also be getting more involved on Instagram this year (@DerekTCarty), if that’s more your thing.  Thanks so much to David Appelman and everyone here at FanGraphs for this opportunity.  I seriously could not be more excited, and I look forward to interacting with you all this season!

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Sounds like a very interesting and very complicated projection system. I have a few questions:

1. How do you decide which factors are relevant to include in your projection system? It seems like with so many factors you would be dealing with issues with “Overfitting.”

2. Is this a statistical model based approach? How are the “final” results compiled?

3. What are some main differences in how you produce your season long projections as opposed to your daily projections?