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Thread: Weighted slugging percentage

  1. #1

    Weighted slugging percentage

    https://www.gcsu.edu/sites/files/pag.../mortensen.pdf

    Thought this was interesting. Will we soon be doing sabermetrics based on the precise level of all of the individual opponents faced?

  2. #2
    BBPro is already doing something like this, with their oppOPS metric, though I don't know how it figures into their WAR calculations, or even if it does.

    This analysis seems flawed, though. Jason Kipnis, with a .379 SLG, is the weighted SLG leader? That would imply that he faced a series of pitchers who were far better on average than those other batters faced. Given that his own teammates, some of whom had a higher SLG, would have faced the same pitchers, that doesn't make sense. To make it even weirder, two of the top 3 pitchers by weighted effectiveness were Cleveland players, whom Kipnis of course would not face at all. And the other three were White Sox pitchers, who would not face their two teammates who were in the top five in weighted SLG. So these batters supposedly faced the toughest pitching, yet they couldn't have faced some of the very best pitchers at all. On top of all that, one of the most effective pitchers listed, Deunte Heath, pitched only 2 innings in 2012!!! Hello?

    In fact, over the course of a season, one would expect pitching quality to average out pretty much. I can understand there would be some relatively minor differences that could be the basis of fine-tuning, sort of like park factors. But surely the differences should not be so large that a player who is not even top 100 by raw SLG is first by the weighted metric. In fact, four of the top 5 by weighted SLG are 50th or lower by raw SLG. Conversely, while the top 3 in raw SLG are all top 20 in weighted SLG, which is reasonable, nos. 4 and 5, Hamilton and Trout, are not even in the top 100 in weighted SLG. This paper has the feel to me of the work of someone who devised an approach that in principle seemed to provide what he was looking for, but who did not then step back and look at his actual results, and ask himself if they made sense.

    In any case, if someone is going to go to all this trouble, it should be applied to wRC+ rather than OPS, which has known flaws which will be preserved even with this weighting system.
    Last edited by Stolensingle; 09-27-2016 at 09:23 PM.

  3. #3
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    Agree with much of what SS said.


    I like the idea behind it but not sure how it can be fully and reliably implemented. They wait until the end of the year to calculate all this I assume. What if a pitcher faces better lineups than another. Faces more lefties as a lefty than the average pitcher. What park do they pitch in? Just so many variables.

    I'd much rather look at rrERA+ and a pitchers allowed SLGeff to help determine his ability. For the hitters I think we have a good idea about slugging, but looking at new angles is always welcomed. It's the only way to get places.
    Last edited by Sultan_1895-1948; 09-27-2016 at 09:14 PM.
    "By common consent, Ruth was the hardest hitter of history; a fine fielder, if not a finished one; an inspired base runner, seeming to do the right thing without thinking. He had the most perfect co-ordination of any human animal I ever knew." - Hugh Fullerton, 1936 (Chicago sports writer, 1893-1930's)

    ROY / ERA+ Title / Cy Young / WS MVP / HR Title / Gold Glove / Comeback POY / BA Title / MVP / All Star / HOF

  4. #4
    Jeff Sullivan recently posted an article at FG in which he points out that Kevin Kiermaier, who gets so much of his value from his outstanding defense in CF, is also underrated because he has faced tougher pitching than the average player:

    http://www.fangraphs.com/blogs/anoth...is-underrated/

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