Analyzing Danny Duffy Part 1: The Numbers

The Kansas City Royals have made it very clear that they have no intentions of being 2018 bad in 2019. In order for the Royals to be any kind of competitive in 2019, Danny Duffy has to return to 2016/2017 form. The Royals need their well-paid ace to take a step forward. In order to figure out how that may be possible, I’m going to spend a couple of weeks analyzing Duffy’s 2018 season to see where there might be room for improvement.

As you can probably tell from Danny Duffy’s 4.88 ERA and 4.06 BB/9, there are going to be several places that Duffy could improve for 2019. I want to start with the walk rate.

After having Tommy John Surgery in 2012 and missing most of the 2012 and 2013 seasons, Duffy posted these BB/9 between 2014 and 2017:

• 3.19
• 3.49
• 2.10
• 2.52

Those four seasons also represent Duffy’s four best seasons as a starter in terms of runs allowed. Seems pretty simple, really. Don’t walk hitters, and you’ll allow less runs. That SOUNDS simple, but let me tell you that throwing strikes while changing speeds and mixing pitches and altering timing and keeping hitters of balance and and and...is very difficult.

There are several mechanical or injury related issues that would cause Duffy’s walk rate to increase by over 1.5 BB/9 innings, but this article is here to strictly examine the numbers. We’ll dive into images later. For now, we’ll just note the walk rate.

There are some concerns with Duffy’s health, considering that he has had Tommy John Surgery and had another minor procedure this past off-season, so I went to look at the velocity on his pitches, the spin rate on his pitches, and the frequency with which he threw his pitches from 2017, his only other full season as a starter in the Statcast Era. Here’s a breakdown:

• Fastball
  2017 averages: 92.9 mph, 2,173 RPM, 16% Whiff%, 47.3% usage
  2018 averages: 93.1 mph, 2,252 RPM, 20% Whiff%, 55.5% usage
• Slider
  2017 averages: 83 mph, 2,313 RPM, 33% Whiff%, 29.1% usage
  2018 averages: 83.3 mph, 2,330 RPM, 27.5% Whiff%, 16.2% usage
• Curveball
  2017 averages: 73.3 mph, 2,343 RPM, 0% Whiff%, 0.7% usage
  2018 averages: 76.1 mph, 2,365 RPM, 25.2% Whiff%, 9.4% usage
• Changeup
  2017 averages: 83.7 mph, 2,410 RPM, 31.1% Whiff%, 22.8% usage
  2018 averages: 83.6 mph, 2,412 RPM, 29% Whiff%, 18.6% usage

Some things to note:

1. Duffy’s fastball was pretty good for him in 2018 and so he used it more than he did in 2017. (I am currently working on ranking MLB pitches but I haven’t gotten to fastballs yet. As soon as I do I’ll have a better idea of just how good Duffy’s fastball really was this year.)
2. Duffy’s slider appears to have been his go to off-speed pitch in 2017. I’ll have to go back and take a deeper look at his success with the slider last season, but his extreme lack of throwing that pitch in 2018 is concerning. I made joke on Twitter yesterday that Houston should trade for Marcus Stroman, fix his slider, and turn him into Charlie Morton. I don’t wonder if Duffy isn’t a couple of small fixes to his slider away from being really really good again.
3. Duffy’s changeup is a real weapon for him when he’s throwing it right. He did not throw it right, at all, in 2018. I don’t think the changeup is more important to fix than the slider, but it certainly wouldn’t hurt. According to my personal data, Duffy’s changeup was a below league average offering in 2018, after being a well above average offering in 2017.
4. The move to throw more curveballs and less sliders is not inherently a bad thing. I am just worried about the “why” involved. I love Duffy’s slider and would prefer to see that pitch thrown instead of the curve.

The raw data doesn’t necessarily give us any clue as to why Duffy wasn’t very successful in 2018. If you look at his velocity and spin rates, the ball is physically coming out of his hand just fine. The raw data on his pitches wouldn’t suggest that Duffy is hurt or otherwise having issues. Clearly though, issues exist. Let’s take a quick look at every major statistic for Danny Duffy that got worse in 2018:

• BB/9
• K/BB
• HR/9
• GB%
• HR/FB
• ERA
• FIP
• WHIP
• BAA
• Hard%
• Medium%
• Soft%
• Swing%
• SwStr%
• Contact%
• Zone%

You get the picture. Pretty much everything that could get worse for Duffy in 2018 got worse. The weird thing is that the raw data, the PITCHF/x data, the pure stuff coming out of his hand, may have actually been better. I would assume that that is not a normal trend for big league starters. I honestly expected to find that the stuff coming out of Duffy’s hand would’ve been down a tick given his results.

This leaves me with a couple of different theories:

1. Duffy’s delivery/mechanics are off.
2. He simply isn’t locating the ball like he did in the past.

I’ll dive into those theories next week. Until then, here’s a little teaser about the type of thing I’ll be looking at: