Duffy's evolving BB/9 over his short MLB career

by kcdc1 on Jul 25, 2011 4:22 PM EDT

There has been a sense that Duffy's command is settling into an above-average range after an adjustment period upon entering the Majors, so I decided to graph the progress of Duffy's walk rates over his 11 MLB starts.

Walk rates stabilize fairly quickly as baseball statistics go such that a sample size of only 30 innings can give you a pretty good sense of a pitcher's command. Plotting each start on its own will show mostly random noise, so I chose to plot a moving average with each data point reflecting Duffy's previous 4 starts up to that point. (The first data point shows Duffy's BB/9 over his first 4 starts, the second data point shows starts 2 through 5, etc) This gives an average sample size of just over 21 innings per data point which isn't a rock-solid indicator of future performance, but should be enough to show real changes in performance over time.

Tweet Comment 20 comments | 2 recs |

Do you like this story?

Comments

What do we think his true talent BB/9 is right now?

The MLB average is a shade over 3 BB/9. Duffy’s average through all 11 starts is 4.12 BB/9. I think this graph strongly suggests that he’s better than that number, but I don’t know how much better. I’d be mildly surprised if Duffy’s BB/9 were worse than league average for the rest of the season.

by kcdc1 on Jul 25, 2011 4:47 PM EDT reply actions

Duffy's last 5 starts

29:6 K:BB

4:1 is elite and he’s almost at 5:1.

Brett Anderson is the Truth. Brett Anderson is divine presence. Brett Anderson is eternal life. Brett Anderson is within you. Brett Anderson is here. Brett Anderson is Now.

by Frederick0220 on Jul 25, 2011 5:11 PM EDT reply actions

I think he's good

But it’s unlikely he’ll sustain that level of success. If he can stay below 2.5 BB/9, a 3:1 K:BB ratio will be within reach.

When I decided to graph this, I expected that it would show his walk rate dropping off sharply after a rough start, but I didn’t expect the trend line to settle in quite as low as it did. If he sustains a 2 BB/9 with his ability to miss bats, he’ll be an ace.

by kcdc1 on Jul 25, 2011 5:20 PM EDT up reply actions

+1

You only see ~5:1 K:BB from Lee, Halladay, Greinke, Verlander, and Haren (Kershaw is getting there).

Brett Anderson is the Truth. Brett Anderson is divine presence. Brett Anderson is eternal life. Brett Anderson is within you. Brett Anderson is here. Brett Anderson is Now.

by Frederick0220 on Jul 25, 2011 5:26 PM EDT up reply actions

I can see Duffy settling in at 8.8 K/9 and 2.2 BB/9 so 4:1 on the dot.

Brett Anderson is the Truth. Brett Anderson is divine presence. Brett Anderson is eternal life. Brett Anderson is within you. Brett Anderson is here. Brett Anderson is Now.

by Frederick0220 on Jul 25, 2011 5:27 PM EDT up reply actions

We can hope....

Realistically, that’s not the most likely outcome, but it’s not impossible either. It’d be nice to have a cost-controlled legit ace for the next 6 years.

by kcdc1 on Jul 25, 2011 5:29 PM EDT up reply actions

Oh, fa sho.

I think he becomes a terrific pitcher. It’s just a matter of when everything falls into place.

Brett Anderson is the Truth. Brett Anderson is divine presence. Brett Anderson is eternal life. Brett Anderson is within you. Brett Anderson is here. Brett Anderson is Now.

by Frederick0220 on Jul 25, 2011 5:43 PM EDT up reply actions

5 HRs tho...so maybe his control has been sharp, but he has caught too much of the plate at times.

I’m a big fan of Duffy, let me tell ya.

Mid-90s gas that plays up even harder with the incredible life, a great changeup, and a good curve (curve has looked better than it did in his debut…still a bit inconsistent, but very good at times).

Also has terrific mechanics.

potential.

Brett Anderson is the Truth. Brett Anderson is divine presence. Brett Anderson is eternal life. Brett Anderson is within you. Brett Anderson is here. Brett Anderson is Now.

by Frederick0220 on Jul 25, 2011 5:23 PM EDT up reply actions

*#1 potential

Brett Anderson is the Truth. Brett Anderson is divine presence. Brett Anderson is eternal life. Brett Anderson is within you. Brett Anderson is here. Brett Anderson is Now.

by Frederick0220 on Jul 25, 2011 5:23 PM EDT up reply actions

if i can see that kinda ratio continue, i'll be impressed...

5 starts doesnt do it for me. affeldt put together a string like that in 2003 along with countless other pitchers

Fire Everyone

by billybeingbilly on Jul 25, 2011 5:24 PM EDT up reply actions

He's pretty good

SBN's most random and mysterious lurker
though I do love Royals Review

by Lum on Jul 25, 2011 5:17 PM EDT reply actions

But he's trending up

by Rowyal on Jul 25, 2011 9:03 PM EDT up reply actions

Good Graph,

shows a trend, but shouldn’t someone be shrieking, “Small Sample Size!”? Duffy had 4.2:1 at Omaha, about 4.4:1 at Springdale.

by Jim Fetterolf on Jul 25, 2011 9:06 PM EDT reply actions

I discussed the sample size issues in the post

The data can only tell you so much, but even with sample limitations, I think it tells a narrative. You can clearly see that Duffy has improved his control after a shaky start. The sample isn’t big enough to tell whether Duffy will settle at 2bb/9 or 3.5bb/9, but it suggests that his control is better than the 5bb/9 he initially showed. It’s probably also better than his 4bb/9 average that is weighed down by his bad early starts.

by kcdc1 on Jul 25, 2011 10:06 PM EDT up reply actions

It’s telling that you read criticisms of your use of statistics as “shrieking.” You frequently draw unwarranted conclusions from very small samples of data and micro-trends. People often point out to you how and why this is a mistake. But you ignore that and just keep making the same mistakes over and over. I have a feeling that you see statistical analysis in baseball as a game where you just hunt for a stat that supports you and throw it out there. In reality, statistics provide very valuable information and sound analysis can be extremely insightful. I don’t think you’re interested in sound analysis. You’re just picking random stats and goofing off. For instance, your use of RSD has to be a joke.

You may know me as NYRoyal.

by Scott McKinney on Jul 25, 2011 11:26 PM EDT up reply actions

tee-hee

And you like to hunt down Fetterolf comments wherever they lie to point out how wrong he is. I get a kick out of both ends.

by kcdc1 on Jul 25, 2011 11:33 PM EDT up reply actions

Also, as long as you're here, what do you think about my statement that Duffy is steadily improving?

by kcdc1 on Jul 25, 2011 11:34 PM EDT up reply actions

Or has improved I guess

I don’t really expect that trend line to continue to negative walks…..

by kcdc1 on Jul 25, 2011 11:35 PM EDT up reply actions

He's certainly improved and you did a good job of showing that

But I don’t know if we can expect him to stay settled down around 2 K/9. He might. But we’re also looking at a trend over just 11 starts. I think it is too soon to tell, but I am optimistic about him. Of course there is a lot of uncertainty there and it’s way too soon to tell that he’s going to make it as at least an average starter in the majors.

You may know me as NYRoyal.

by Scott McKinney on Jul 26, 2011 12:02 AM EDT up reply actions