Wednesday, July 16, 2008

Brewers Struggle Against Bad Pitchers?

Miller Park. The local watering hole. My brother-in-law's house. No matter where I've been lately, it's always the same. If a conversation is struck up about the Brewers' chances of a post season appearance this year, it never seems to take long before someone says, "Yeh, if they can just figure out how to hit bad pitchers." So ingrained in Brewers lore is this belief that evidence supporting it isn't even necessary. Everyone knows it's true, right?

Well, as the resident skeptic of all things assumed in baseball, you'll have to excuse me if I want to see if the facts support the theory. But how do we do that? The first thing we need to do is define what exactly a "bad pitcher" is. Is it a starting pitcher with a bad ERA at the time of his start? Not necessarily, as a pitcher with a 6+ ERA in June may not really be that bad of a pitcher. ERA just can't be trusted over a short period of time. We need something better.

What we really need to use is an updated ERA projection for each pitcher, which is our best guess at their true ERA (their ERA without the sample error). Now, I could use this method to update each of the pitcher's 2008 Marcel projected ERA to account for their performance this year but that's a little too much work. I'm going to do it a bit more crudely. I'll simply take a weighted averaged of their 2008 Marcel projection and their 2008 ERA. The exact weight I used is dependent on the number of innings each pitcher has worked this year but it works out to roughly to a 70/30 split for most pitchers. Not perfect but good enough for the task at hand.

Now, all all we have to do is find the worst projected starting pitchers from the first half of the season and see how the Brewer batters did against them. Here's every start against a pitcher with a projected ERA over 4.75:

In 19 games, the opposing starters had an updated projected ERA of over 4.75. Their average projected ERA (weighted by the IP of their appearances) was 5.12. Brewer batters hit them for a 5.42 ERA. The Brewers batters feasted on bad pitching!

But hold on a second. Of those 19 starts, the Brewers only beat the projected ERA in 8 of them. That's terrible, right? Not really. When a bad pitcher gets tagged for 5+ earned runs (as they invariably do at least a few times a year), it doesn't take many of those kind of starts to kill their ERA. Bad pitchers still have plenty of good starts. Let's look at a couple of the worst pitchers on that list. Josh Fogg? 5.01 career ERA. Despite that, in 42% of his career starts, he gave up 2 or less runs (min. of 5 IP). Mark Redman? Career ERA of 4.85. 2 or less earned runs in 5+ IP in 43% of his starts. A quality start, 48% of the time. That shouldn't be surprising, though. That's just how baseball works.

And for anyone who thinks that projections are the work of the devil, the Brewers have done fine against pitchers who have a bad 2008 ERA as well:

It's frustrating to watch a starting pitcher with a bad ERA do well against the Brewers but it happens to every team fairly often. That fact may not make it easier to watch but it's certainly not unexpected. So the next time you hear that Brewer batters stink against bad pitchers, send them this link!


Post a Comment

<< Home