The New and Improved Danny Duffy. He’s back with a… Curveball?
In 2016, I made a case that Danny Duffy was finally displaying the results that matched his talent. Duffy was mixing his 95 mph heat with fewer walks. That recipe was a success and the Royals’ burgeoning Ace worked his way to a 3.64 ERA between 2016 and 2017. Before 2017, the Royals gave Duffy a 5 year, $65M deal to stick around the rotation for a while in a deal that I dubbed decidedly team-friendly. Well, he’s regressed in 2018 and the “team-friendly” deal is now another in the Royals’ long list of worrisome developments.
But Wednesday, June 27th just happened. Duffy pitched really well on Wednesday, June 27th, 2018. This is noteworthy because of just how bad Duffy had been in 2018 on the whole. The lefty had a 5.18 ERA (7th worst among qualified starters in the Majors), a 1.51 WHIP (6th worst), a 5.43 FIP (3rd worst), and was among the worst at giving up homers and walking batters. It’s that last bit that is especially worrisome. You see, my hypothesis in 2016 was simple for Duffy: Walking fewer guys = fewer guys score. The data since then seems to back up the point:
But pitching is not as simple as simply saying “don’t walk anybody.” Duffy is throwing just 3% fewer pitches in the zone this year than last, but is that difference in walk rate really reflective of 3%? I doubt it. Duffy is sporting largely the same repertoire in terms of a fastball just a hair under 94, and sliders, changeups, and sinkers that are roughly all the same pitches. What gives?
Two minor things jump out from pouring over his data. First, his pitch usage.
| 2017 | 2018 | |
| Fastball | 47.4% | 55.8% |
| Slider | 29.4% | 21.1% |
| Change | 22.7% | 20% |
| Curve | 0.5% | 3% |
He’s throwing the fastball more at the expense of the slider. His slider in 2017 was a great pitch, but as the table below shows, it has not been as good in 2018. The table below is his wOBA allowed on each of his primary offerings.
| 2017 | 2018 | |
| Fastball | .349 | .360 |
| Slider | .259 | .367 |
And the data and eye test around the slider show that it’s a different pitch than it was in 2016 and 2017.
The second major point is that his release point is slightly different in 2018. His arm slot is slightly lower (by like an inch), and thus, his release is slightly closer to first base. Fixing the release point may be the trick to regaining the slider, but the release point is such a minor detail that it’s likely just a case of the author searching for an answer, rather than identifying a problem.
Wednesday, June 27, 2018
I mentioned in the outset that things may have changed yesterday. That was a bit of an overstatement. Duffy’s last 7 games have been quite effective (2.68 ERA), but the last two have seen a dramatic increase in usage of his curveball. This is a simple case, really. Since the slider is no longer getting people out, it’s time to switch to something else.
But we can tell that he’s basically just substituting the curveball in for where he used to throw his slider. It’s a welcome development for Duffy fans. The pitch isn’t particularly effective, but it gives hitters something else to consider and feels like Duffy embracing “crafty lefty” status as he approaches 30.
There have been rumors that Duffy may be shopped as the Royals look to accelerate their rebuild. With 3 and a half more years of team control, and his recent turnaround possibly outweighing the ugly season-long numbers, the Royals would be wise to at least check on the possible return that Duffy could yield. His performance once looked to be an Ace in the making, and then he looked more like a good #3 starter in 2017 before starting the year off as one of the worst pitchers in baseball. He’s back to pitching like an Ace recently and there is room for improvement if he can figure out a way to minimize the walks.
-Sean Morash
