Examining the Wizard: Roy Oswalt's DIPS ERA

by Stephen Higdon on Aug 21, 2008 3:12 PM CDT

I need to preface this with: I'm not 100% that the DIPS ERA I'm about to report is perfect. I am still waiting on a data set from 2008 that I purchased to help me correct some possible differences in batted ball results from the 2006 data set I was able to find online. However, I don't expect that margin of error to be more than 3 runs, which over 150 IP (where Roy Oswalt is now) is only a difference of is a +/- .198 ERA points. So you can keep that in mind as you look at this.

Using the method that I outlined in Baseball Knowledge 201: DIPS > ERA, and data obtained from FanGraphs.com (it's linked below), I broke down Roy's batted ball data to correct for a lower line-drive rate and his slightly inflated HR/FB rate. I'm uploading a spread sheet that you can play around with that has all the information and calculations I performed. All the nitty gritty of the math is on the there. Anyone with a firmer grasp of the Base Runs formula, please feel free to chime in on where I screwed up -- if I did (crosses fingers).

The result was surprising to me, at first. Using the DIPS 3.0 methodology, I determined that Roy Oswalt owns a DIPS ERA of 4.85. My jaw dropped and I went back over all the math and the spread sheet formulas about 10 different times when I saw that. I recalculated the batted ball averages and read every article I could find on Base Runs. I was left with the same number. Then it occurred to me that I should stop disbelieving and start hypothesizing.

These are the things we know about the Astros and Roy Oswalt (Source and Source):

They have the second best team RZR (click if you're unfamiliar with RZR)
They have the best infield RZR.
They are slightly below average in outfield RZR, but Bourn and Pence are the cream of the crop in the respective positions for RZR. So we basically have a 2/3 of an stellar outfield; with Bourn probably taking at least 1/12 of Carlos Lee's territory.
Roy Oswalt's In-field fly percentage is down (6% compared to a career rate of 11%).
Roy Oswalt's LOB% is also well below his career levels (72.8% to 76.5%)

So what do all of those things mean? Mostly it means that because the Astros defense is so far above league average, that a DIPS ERA will naturally be inflated, because correcting his line downward. Further, it means is that even though Roy has a great defense behind him, he's not taking advantage of it by pitching well with men on base. As result, he's raised the rate at which he is facing batters. The more batters he's facing, the more likely his is to allow ball to be put in play and the more balls are put into play the worse things get. Interesting to note, that if his results were in fact league average, we'd expect on 17.5ish HR against him. That last two points are should be alarming for Astros fans.

The reason I am truly excited to get my hands on the 2008 batted balls data set, is so that I can break up Roy's batted ball data to pre and post ASB splits. With this, I am hoping to see that Roy really was just a bad pitcher when he had a irked hip. Once he rested and rehabed, Roy has really returned to form. My hope, actually all of our hope's should be, is that Roy's split DIPS ERA will show that luck wasn't to blame for his awful start, but bad pitching. While people far more skilled at database coding than me will have to determine if he was ineffectively pitching from the stretch using pitch/fx, I think that might be the conclusion we can reach; if the numbers confirm my hypothesis. This would be good news for Astros fans.

Like I said, I'm not fully sure of that all of the numbers are perfect, but the margin of error should be relatively minor. To repeat, I urge those who want to check my math to do so and also throw out their own hypothesis about why it is that Roy's DIPS ERA is .75 runs higher than his actual ERA?

Here is the roydips3.0 (excel) spread sheet in Excel. If you want it in CSV post your request in your comment and I'll shoot it to you in an email.

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Comments

There are some good things from Roy’s season. His K/BB rate is up, for instance. But if this is adjusting for his ridiculous HR/FB rate, then we might have some problems. Hopefully, as you say, looking at his post-June starts will show that he’s returned to form.

by Only_A_Lad on Aug 21, 2008 5:01 PM CDT reply actions

His command has been great and his K rate is up a bit.

No one thought that would happen. I think the reason for the disproportionately high DIPS is that the Astros defense is so far above league average this year that a DIPS ERA would naturally be inflated. I didn’t do a good job of stating that in the post. I’ll edit the post to reflect that, but everyone will know I screwed up because of this.

That said, if Roy’s ASB splits don’t indicate a return to excellence, we could be in for some trouble if the defense lapses next year.

A good friend of mine used to say, "This is a very simple game. You throw the ball, you catch the ball, you hit the ball. Sometimes you win, sometimes you lose, sometimes it rains." Think about that for a while.

by Stephen Higdon on Aug 21, 2008 5:28 PM CDT up reply actions

I should clarify "no one thought this would happen"

I thought, as I am sure most of you did, the downward K/9 was from his public statements that at the beginning of 2007 he was trying to pitch to contact with Adam Everett behind him. He had a noticeable split stat for his K/9 before and after Everett got run over by Carlos Lee, which is why I was surprised that most of the “experts” thought his K rates were set for a further decline.

by Stephen Higdon on Aug 21, 2008 5:40 PM CDT up reply actions

I hadn't thought of that.

It’s something of an interesting statement on Roy as a pitcher. A lot of guys wouldn’t be willing to trust their defense, even with someone like Everett behind them.

Even if Oswalt’s HR/9 rate is up, however, I wouldn’t be too worried. We tend to think of HR/9 to be a “true ability” like K/9 or BB/9, but home runs vary so wildly by year that even much of this season’s totals might just be noise.

His injury has obviously exacerbated that, though. And his early season struggles hurt his numbers for this year more than we might remember. Remember that the first few months of this season, he slumped pretty hard. He had that one start against Florida in which he gave up four homers. If you take that start out of the equation, then Roy’s HR/9 rate drops to 0.99 – not exactly pretty, but not as awful as it is now.

We should probably just give him a mulligan on this season. We’ll see how he feels next Spring. If he struggles then, we actually will be having real problems. But if the last start (small sample size, I know) is any indication, and we all hope it is, then Roy will be just fine.

by Only_A_Lad on Aug 21, 2008 6:48 PM CDT up reply actions

And with that said,

The best thing for Coop and Wade to do with Roy is just shut him down for the season. Let him pitch the next start against Santana, but it’s stupid to risk an injury to our only good pitcher on a meaningless game.

by Only_A_Lad on Aug 21, 2008 6:52 PM CDT up reply actions

I haven't made any calculations...but I take the somewhat simpler approach...

of looking at the stats in the Hardball Times. Roy O’s Defense Efficiency Ratio is actually down from previous years (.680 vs. .698 in the Adam Everett prime years); so that doesn’t seem to indicate that he gained much from the Astros’ defensive improvement this year. (I’m not saying that DER is the greatest defensive stat in the world, but just pointing it out..) His FIP isn’t bad, and is better than his ERA (4.10 vs 4.26). The only stats which are aberrant is a somewhat lower than typical Groundball Rate and and the HR/Flyball rate. Adjusting for the HR/Fly rate, the x-FIP is good, 3.72.

My working theory is that Roly Oswalt has been affected by a recurring muscle injury in his hip and that it caused the sporadically bad performance. (Even though Oswalt denied that injuries affected him earlier, he now says that he is pitching better because he is “finally healthy.”) Now that he seems to be over that problem, he is finally pitching like the normal Roy O.

by clack on Aug 21, 2008 6:57 PM CDT reply actions

We have the same theory.

I’m glad you put the qualifier on DER, because it’s essentially 1-BABIP, and BABIP isn’t necessarily an indicator of much. If it’s high are low, it’s merely indicating that you need to dig deeper to find why it’s high or low (i.e. is it poor performance or luck?) FIP is ok, but it doesn’t have very strong correlations with next year’s ERA, where as DIPS 3.0 has a year to year correlation of .8-ish. It’s because it is simplified, which is easy, but that’s not always better. This is mainly because it depends mainly on BABIP, all you need to do to have a good FIP is have good Strike out and walk numbers. DIPS captures much more than FIP, making it the more telling of the two.

His GB% is down a mere .2, where as his FB has declined, but that’s pretty much due to an increased LD, which you can see in the spread sheet. What’s hurting him are the long balls, the LOB, and the to corresponding increase in batters faced. The only way Roy’s DIPS ERA could deviate in a negative direction from his ERA would be if he’s gotten lucky all season long (he hasn’t) or if he’s pitched poorly. If we know that the Astros defense is one of the best in the league then we’d expect his ERA to be lower than his DIPS ERA (it’s defense independent, so whatever advantage he’s received from his defense are erased). What his high DIPS ERA tells us, is that Roy has pitched poorly this year.

Like I said, I’m waiting on a data set to be able to manipulate the numbers into the split stats to see if we can blame this all on a nagging hip injury. I hope that’s what the numbers tell us.

by Stephen Higdon on Aug 21, 2008 9:22 PM CDT up reply actions

good points...

I should have mentioned “line drive rate” when I said that only two stats were aberrant.

by clack on Aug 22, 2008 7:56 AM CDT up reply actions

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