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Expected Win-Loss Record (X W-L) – Chris Flannery

Expected Win-Loss Record (X W-L)

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Major League Baseball now posts (since mid-2006) a new stat:

X W-L – Expected won-loss record based on runs scored (RS) and runs allowed (RA), using this formula: RS^1.82/((RS^1.82)+(RA^1.82))

… what does this tell us?

Seemingly this stat can tell you how teams win, if the X W-L ratio greater than the actual W-L ratio the team loses close games but wins big, or if less than the team is winning close but losing big.

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for the real math behind it, check out this 1999 article form Baseball Prospectus

In practical terms, the implications are fairly small. For most off-the-cuff calculations of runs and runs allowed into wins, the 1.5% gain in accuracy isn’t worth the trouble of finding a new exponent for every team; just use 1.85 or thereabouts, and get on with your life.

It really makes a difference, though, to the small group of people who try to assess the value of a player’s performance as precisely as possible.

The most noticeable impact is going to be on the value of good pitchers in extremely pitching-friendly environments. A pitcher-friendly environment brings down the exponent; a good pitcher, by his own efforts, decreases the run environment and the Pythagorean exponent even further.

continue on for a good Bob Gibson example

Honestly, I don’t see how this helps anyone understand anything.

[tags]MLB, baseball, stats, X W-L[/tags]

7 thoughts on “Expected Win-Loss Record (X W-L)”

  1. I agree with Chris… this one doesn’t mean much to me. Maybe we should rename it from ‘ExWL’ to ‘WTF’. 🙂

  4. I like it. It’s why looking at WHIP is important and not just looking at ERA or W-L records of pitchers. It gives you a sense of how tough the team you’re facing might be, since the W-L could be misleading. Sounds like FanGraphs may have an even better formula in their wRC, but I’ve only just read about it now.

  5. This stat is crucial to WAR meaning anything. It’s also an interesting stat in that it aims to say which team would have a better record in a “million game season”. Or said another way which teams may actually be better or worse than their record indicates. I don’t think you are using it correctly. The result of your calculation to explain expected win-loss record is a number. The result would be one number. The stat is actually a “record” such as 60-47.

  6. Why is MLB trying complicate a simple game. Teams either win or loose. The only time this stat comes into play is during the playoffs. If teams win a lot 1 run games, then they might struggle in the playoffs or if teams win big then they might close opponents out early, but it doesn’t matter. Baseball is funny that way. The good teams have balance and the streaky teams rely on mistakes. Solid playoff teams have a combine great defense, really good starting rotation (1-3) and key hitters who take advantage of poor pitching. I have always said this about baseball, leave it alone. Stats are good for history not to build a team.

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