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The Astros Pitching Implosion

Most Astros fans know that the Astros pitching has not been good in the second half of this season. I will confess; even I did not know it has been this bad for this long. When did the Astros pitching implosion really start?


Today, I put out a Twitter poll asking

poll

Folks, before writing this article I would have agreed with the plurality in this poll that the pitching got mediocre in July. Here are the Astros pitching numbers by month.

At the end of June, the Astros led the league in ERA with a 3.58. That concealed the fact that IN June the pitching ranked 17th in the MLB at 4.20 ERA. It has been mediocre or worse since.


Some wonder why I always talk about FIP instead of or in addition to ERA. The chart above illustrates that the FIP, even in April and May, was NOT as good as the ERA and has been warning us all season that the ERA was unsustainable. Here is a graph of the ERAs, FIPs, and xFIPs by month.

S0, what happened? Let's deep dive into some data.

I know that is a lot of data to absorb. Remember the heatmap methodology- red is good, blue is bad. Let's explore some of the graphs to see if the trends give us some answers.


For most of these graphs the scale has been set where the center of the graph is close to league average and the scale is set to 10% above and 10% below average.

Astros pitchers started GREAT at preventing hits and were close to average in May, June, and July.

The OBP trend is similar to the hit trend- great early, bad in June through August. WHIP obviously follows this trend.


Power

Average MLB ISO is 0.166. The scale on THIS graph was set to -20%/ +25%.

Astros pitching was GREAT at preventing extra base hits in April and May. In June, the team became worse than average, and it got worse in July and August. In September, the Astros have been horrible!


Walks and Strikeouts

Like the other trends the strikeouts dropped dramatically in June. In July, August, and September, the strikeouts have hovered around average.


At the same time, the walks jumped significantly. June, July, and August were bad months for walks.


Let's look at the combination of keeping batters off-base and limiting their power. This can be modelled in OPS allowed and wOBA.

As expected, both are great in April and May. In June, things degraded significantly and got worse in July.


If one evaluates the relative ranks for hits, walks, power, and strikeouts; the Astros pitching staff looks like this.

Walks started getting worse in May actually. They were near the worst in the league in preventing walks in July and August.


Power prevention got bad in June and became a HUGE problem in September.


Strikeouts started off great in April and May. They fell off in June.


It is hard to understand how a team that started so well has become so bad. Next time we will go pitcher by pitcher to understand how each have impacted this drop off.


The answer to when the Astros pitching became mediocre is June. but how the implosion has hit the pitching staff is multifaceted. It is not easy to see how this staff can or will recover this year.


Overall, September's metrics would be better IF the team could limit power. That is at least step one for the Astros right now.



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