An Intro to THE BAT by Derek Carty January 23, 2019 What’s up, FanGraphs! My name is Derek Carty, and I’m pumped to announce that my projection system, THE BAT, is back at FanGraphs for its second season! If you’re into DFS, you may have heard of THE BAT. I’ve been building this system for the past eight years, and 2019 will be the sixth season it’s been available publicly, first at Fantasy Insiders and now at RotoGrinders. Last year I brought THE BAT season-long projections to FanGraphs, a recent article by Ariel Cohen (which was nominated for FSTA Article of the Year—congrats!) with some really unique methodology showed it to be the most valuable of all the non-aggregate projection systems that were tested by a large margin. As for who I am, you may recognize me from my time managing the fantasy sections for Baseball Prospectus and The Hardball Times way back when. The past half-decade or so I’ve been focused solely on daily fantasy sports and sports betting, most notably with ESPN.com, Baseball Tonight, RotoGrinders, and on Twitter (@DerekCarty). I’ll also be experimenting with some cool, exclusive content on Instagram (@DerekTCarty) starting in March. 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 last year, THE BAT had 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 the effect of humidity on air density 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. 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 in a couple weeks! It’s how I’m able to bring the season-long version to you here at FanGraphs as a free-of-charge “thank you”! If you have any questions about THE BAT or really anything baseball-related, please feel free to drop a comment here, tweet at me (@DerekCarty), or find me on Instagram (@DerekTCarty). Thanks so much to David Appelman and everyone here at FanGraphs for having THE BAT back for another year. I loved interacting with you guys last year and hearing how well you all did in your fantasy leagues, and I look forward to another great season!