FanGraphs Baseball


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  1. Aren’t the numbers skewed against offense, too, because there are also “inferior non-MLB” hitters are batting? Wouldn’t it be better to look at AVG/OBP/SLG/wOBA for hitters that were already in the majors before September?

    Comment by Julian — September 24, 2012 @ 1:07 pm

  2. Interesting study, but the data might be skewed due to the inclusion of the September call-ups themselves. It makes sense that a bunch of minor league players getting a fair number of plate appearances against major league pitchers would cause offense to drop, especially if you believe that the gap between AAA and MLB pitchers is bigger than the gap between AAA and MLB hitters.

    I’d like to see two more versions of this study, one showing offensive performance for the league excluding hitters who were added in September (but including PAs against pitchers added in September), and one showing pitching performance for the league excluding pitchers who were added in September (but including PAs against hitters added in September). I’m guessing that data would be a lot harder to compute, though.

    Comment by Ian R. — September 24, 2012 @ 1:10 pm

  3. This is the big one. Also should try to tease out the effects of cooler September weather. On the small side, I’d wager. But don’t begin to know till you account for it.

    Comment by Richie — September 24, 2012 @ 1:18 pm

  4. Cooler and less humid.

    Comment by swieker — September 24, 2012 @ 1:19 pm

  5. Needs to be re-run for only players who had 200 PA (or some number) pre-September.

    Comment by drewggy — September 24, 2012 @ 1:23 pm

  6. Good piece, and the previous commenters make helpful suggestions for next steps. I would add that looking at measures of variance/dispersion would help to contextualize these numbers. Simple chi-squared tests can indicate if the variance is significantly different in September than in the rest of the season. If variance increases but the mean stays the same in September means are the same, then you have a decent indicator that the “win at all costs” and “play the kids” approaches actually are happening, and are canceling one another out.

    Comment by Taylor — September 24, 2012 @ 1:27 pm

  7. Expanded rosters also mean fewer plate appearances to go around. Doesn’t pinch hitting and a lack of consistent abs tend to drag down offense as well?

    Comment by DTF_in_DTL — September 24, 2012 @ 1:39 pm

  8. This is smart.

    Comment by Tyler — September 24, 2012 @ 1:44 pm

  9. It’s also worth noting that injuries may have a bigger impact in September than in other parts of the season, for two reasons: Many good players (especially good, young pitchers) are shut down or given extra days off in September to preserve their health, and many other good players play through injuries for teams in pennant races instead of yielding to a healthier (and potentially more effective) backup.

    Comment by Ian R. — September 24, 2012 @ 1:46 pm

  10. Exactly, this is the problem with the “steroid era” being blamed for all of the crazy numbers of the late 90s early 00s it ignores the elite pitching numbers of the Pedros, Clemens, and Madduxs of the world. Individual HOF type players like Barry Bond’s had great seasons and there were occaisonal Bret Boone or Brady Anderson types but league wide it isn’t like HR/PA spiked. This study ignores that rookie hitters and batters are being added at the same time. Looking at the Sept splits of elite batters seems like a better plan.

    Comment by Tomcat — September 24, 2012 @ 1:49 pm

  11. Thank you, thank you, thank you.

    Many just seem to assume that September call-ups create offensive advantages and that teams out of the playoff picture have the tendency to dog it, giving a huge advantage to playoff teams that play them. Ask Detroit about that idea with reference to Minnesota.

    One thing doesn’t change a bit: on any given day a bad team playing well can beat a good team playing poorly. Scheduling inequities have a much bigger impact on standings than September call-ups, which overall may have little to no impact.

    Comment by PackBob — September 24, 2012 @ 2:02 pm

  12. Yes, this seems blindingly obvious. I have no idea why Dave didn’t do this.

    Comment by AustinRHL — September 24, 2012 @ 2:12 pm

  13. Observational data, not backed by any statistical analysis.

    If there’s any effect, it’s going to be very very small probably too small to see. Half the teams are in playoff contention, at least at the start of September. A lot of non-contending teams seem to feel an obligation to play their best team against contending teams. For certain in the first group, and likely in the second group, those teams are using expanded rosters to improve the quality of their pitching. As Dave noted, playing matchups, and I’d think resting their best pitchers in blowouts and I think getting quality innings from players whose ETA is “next year”. For every crappy starting pitcher who gets hammered, there’s an Erasmo Ramirez who is pretty good in part because none of the hitters have seen him before.

    So really you’re talking about games in which both teams are out of playoff contention and one happens to be using a AAA pitcher. While a few pitchers get shut down in September, it’s not like every team is shelving their top 3 starters and best couple of relievers to go with a AAAA or AAA pitching staff.

    It’s just small sample size.

    Comment by Adam Stein — September 24, 2012 @ 2:25 pm

  14. What a silly article.

    Comment by channelclemente — September 24, 2012 @ 2:52 pm

  15. On the podcast today, Dave explained his reasoning as being, basically, “well, September callups are mostly pitchers, so much more playing time goes to the pitchers than to the hitters.” Obviously, the strawman-like point he’s arguing against is still basically wrong, and he’s probably right that Major League hitters don’t see their numbers go up much in September. But I just don’t think he has any excuse for making such a gigantic assumption.

    Comment by AustinRHL — September 24, 2012 @ 6:40 pm

  16. I’m with you, cc.
    I’m embarassed that I actually read the whole article and the comments.
    I guess I was really bored.

    Comment by Baltar — September 24, 2012 @ 7:19 pm

  17. Maybe looking at the splits for only the hitters on teams with a winning record on September 1 (or within X games of a playoff spot) would show us something…

    Comment by Matthias — September 25, 2012 @ 1:06 pm

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