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Old 07-13-2018, 10:50 PM
FlikTheBlue FlikTheBlue is offline
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Does run differential in baseball indicate if a team is just lucky?

Is it a good assumption that baseball teams with good W-L records but not so good run differential are just lucky rather than good? Iím thinking in particular of this yearís Seattle Mariners. They are currently sitting 22 games over .500 and only 3 1/2 games behind the Houston Astros. Looking at the run differential, however, shows the Mariners basically even in the runs scored vs. allowed, while the Astros are + 183. Does this mean the W-L records are deceptive and that the Astros are actually a much better team and that the Mariners have just been really lucky so far this year?
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Old 07-14-2018, 02:11 PM
Jim's Son Jim's Son is offline
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The chances are pretty good they are lucky and will have a major cold streak later. Sometimes a team will have a good year despite a poor run differential. The 1984 Mets were 90-72 despite giving up 24 more runs than scoring. Sometimes luck, sometimes a good bullpen, sometimes a good manager (Earl Weaver's Orioles teams were good for usually winning more games than the runs scored vs allow equations predicted).
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Old 07-14-2018, 03:15 PM
Chronos Chronos is offline
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But number of runs can be the result of luck, too. When Mighty Casey comes up to bat, it's up to him whether he hits a home run or not. But if he does hit a homer, it's not up to him whether he scores 1 or 4 off of it.

IIRC, the single-best stat for how good a team really is is on-base percentage.
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Old 07-14-2018, 03:43 PM
Snarky_Kong Snarky_Kong is offline
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Not a baseball guy, but I'm quite sure that I've read Nate Silver or some other sabermetrics guy mention that run differential is much more predictive of future success than W-L record. Not sure how on-base percentage compares.
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Old 07-14-2018, 04:24 PM
borschevsky borschevsky is offline
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Basically, yes. Thereís a formula called the Pythagorean Expectation, which calculates how many wins a team should have based on their runs scored and allowed. Itís better for predicting future results than just looking at wins and losses.
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Old 07-14-2018, 10:31 PM
RickJay RickJay is offline
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Quote:
Originally Posted by Chronos View Post
But number of runs can be the result of luck, too. When Mighty Casey comes up to bat, it's up to him whether he hits a home run or not. But if he does hit a homer, it's not up to him whether he scores 1 or 4 off of it.

IIRC, the single-best stat for how good a team really is is on-base percentage.
The meaure of an offense is run scored. On base percentage is simply a component of that; power has a lot to do with it, too.

A team can get lucky in terms of the number of runs it scores, but over the course of 80-100 games, which where we now are in 2018, that evens out pretty quickly.

Run differential is an excellent prediction, at least in the short term, of team performance. You'd be well advised to bet on teams that have been unlucky in this regard to improve, and vice versa. It doesn't always work out but it's where the smart money is. That said, sample size matters. If a team in April is 7-9 with a positive run differential, that means very little.
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Last edited by RickJay; 07-14-2018 at 10:31 PM.
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