May 30, 2011

Fantasy Beat

Carty in Context

by Derek Carty

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Greetings, BP readers.  I’m Derek Carty.  For the past four years, I’ve been managing the fantasy section of The Hardball Times.  It was a terrific run and an amazing experience, but when Baseball Prospectus asked me to manage their fantasy section, I came running.

Aside from THT, I’ve also had my work published by NBC’s Rotoworld, Sports Illustrated, FOX Sports, and USA Today, among others.  In my three years competing at the highest level of fantasy baseball, I’ve managed to win two national titles with four top-three finishes.  In 2009 I won LABR, making me the youngest champion in the history of the longest running league in existence.  I’ve also had the honor of graduating from the MLB Scouting Bureau’s Scout Development Program (“Scout School”), one of two active fantasy writers to have done so.  Most of my writings slant towards the quantitative side of the coin, but I’m of the firm belief that in order to get a complete picture of a player’s abilities, we need both statistics and scouting.

Over the coming weeks, I’ll be announcing some changes for BP Fantasy which should add to the already tremendous crop of writers and features that I’ve inherited.  I’m always open to hearing your ideas and getting feedback about what you like, don’t like, and would like to see, so don’t ever hesitate to get in contact with me.  BP Fantasy is first and foremost for you. I try to make myself as available as possible to fill requests, answer questions, and give fantasy advice.  I’ll be hosting a live chat here at BP on Thursday, but you can get in touch with me via e-mail, Facebook, or Twitter.  If you’d like to learn more about me or read some of my previous work, you can check out my personal website, DerekCarty.com.

One of the most important things I stress when it comes to fantasy baseball is that context is everything.  A win is not a win, and a home run is not a home run.  The context under which an event happens is what is important.  It doesn’t matter if Ramon Santiago has a seven-home-run game if the opposing team decides to pull a Rookie of Year-esque publicity stunt and puts a 12-year old on the mound.  Obviously that is pretty unlikely to happen, but this extreme example illustrates my point well, and there are many similar (if less ridiculous) real-life examples.

Fantasy baseball is, in large part, about predicting what players will do in the future, and context plays a big part in this.  A home run that a lefty hits in Yankee Stadium tells us much less about his future prospects than if he were to hit it in PETCO.  A ten-strikeout shutout against the Reds is much more impressive than a ten-strikeout shutout against the Padres.

There is one particular example that I’d like to talk about today: run environment.  Elsewhere around the web, fantasy writers are talking about how Pitcher A is pitching better this season because his ERA or his FIP or his xFIP is lower than it was last season, ignoring the context under which those numbers were posted.  Take a look at how league average ERA has changed:
 

That is very drastic.  Over the course of two seasons, league average ERA has decreased by half a point.  And since FIP and xFIP are usually presented on the same scale as ERA, they follow the same pattern.

You see, while he have it ingrained in our heads that a 2.00 ERA is fantastic, it’s really only fantastic if the rest of the league is posting a 4.00 ERA.  If the rest of the league is pitching to an 0.50 ERA, that 2.00 ERA isn’t so special after all.

Let’s look at an example.  Chad Billingsley’s xFIP over the past three years have been 3.99, 3.67, and 3.43.  In the absence of context, one might crow that Billingsley has been improving steadily over the past three years and has been pitching at a near-elite level this season – a level deserving of a 3.43 ERA.  This, however, is not true.  You see, once we normalize for the run environment, we see that Billingsley has been almost exactly the same over the past three years, according to xFIP – about ten percent better than league average.
 

This kind of knowledge can be very valuable to fantasy owners in a season where the run environment is so much different than in years past.  A savvy fantasy owner will take advantage of this, attempting to trade a pitcher like Billingsley whose performance relative to his peers hasn’t changed but whose performance appears to have improved dramatically.  If you know that your leaguemate uses ERA, FIP, or xFIP to evaluate pitchers, he is someone that it might be worth trying to peddle your pitchers to.

One last interesting thing to note is that BP’s proprietary SIERA metric hasn’t seen quite the same pattern as ERA and xFIP (SIERA isn’t scaled to ERA like xFIP is).
 

For SIERA, we see that the drop-off came from 2009 to 2010 and that it has stayed the same from 2010 to 2011.  The point still stands that year-to-year SIERA comparisons need to be made within the proper context, but making straight comparisons between 2010 and 2011 should be fine because they share the same league average.

That wraps it up for today.  If you have any questions, as I said in the top half of this article, I’m always available.  Feel free to comment or get in touch with me off-site and I’d be happy to help you with whatever you need.