Going into Spring Training, the big question among Royals fans was “what were the Royals going to do with Danny Duffy after 2021?” Though Duffy has played his entire MLB career in Kansas City, helped the Royals win two pennants and a World Series title, and is currently 22nd all-time in Royals team WAR, according to Baseball-Reference, the future still seemed hazy for Duffy at the surface level.

For one, Duffy’s contract is set to expire after 2021, and with the signing of Mike Minor, along with the abundance of pitching depth in the Royals farm system, it didn’t seem like it would be in the Royals’ best interest to sign him to another extension, especially at 32-years-old.

Second, Duffy from 2018-2020 demonstrated signs of regression on the mound from 2018-2020, as he posted FIP numbers of 4.70, 4.78, and 4.75, respectively, over that three-year span. While those are not terrible numbers by any means, they didn’t exactly encourage Royals fans that he could continue to be a long-term option in the rotation, especially after averaging less than six innings a start over that time span as well (which included a 5.1 average a year ago during the shortened season).

Thus, there were many Royals fans out there thinking that if Duffy wanted to make any case to stay in Kansas City beyond this season, he would need to make a transition to the bullpen at some point in 2021.

However, much to the surprise of most Royals fans, Duffy has been the best starter so far in the Royals rotation, and he’s demonstrating that he not only has stuff in the tank to continue to succeed as a starter in 2021, but also perhaps for another year or two after this year.

Now, will the Royals actually do it? It’s still early, and we only have 18 innings of data on the “Duffman”. That being said, let’s take a deep look at some of Duffy’s metrics and some things to pay attention to in his future starts this season (and how they could impact the odds of him staying in Kansas City after 2021).

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Duffy and his “improved” fastball-slider combo

Duffy introduced a slider to his arsenal in 2017, and it became his primary pitch in 2017, as he threw it 29.1 percent of the time, which was 4.4 percent higher than his fastball that season. However, after that season, Duffy went back to making the four-seam fastball his primary pitch, as evidenced by the graph below:

Additionally, not only has Duffy decreased his usage of the slider since 2017, but he also has decreased the usage of his other secondary pitches (specifically sinker and curve) in favor of a higher usage of four-seam fastballs. That being said, his fastball and slider have often been indicators of overall performance for Duffy in a given season, as evidenced from Duffy’s pitch run value data from Baseball Savant.

In 2017, Duffy posted a run value of -2 on his slider, highlighted by a whiff rate of 32.8 percent. However, that season, his fastball was pretty lackluster, as it posted a run value of 4 and a whiff rate of only 16.2 percent. Thus, it is not a surprise that Duffy utilized his slider more that season over his four-seamer.

However, in 2018, the pitches were inverse on a run value end. Duffy’s four seamer was really good, as he posted a -8 run value and a whiff rate of 21.5 percent on the pitch. As for his slider though, he saw a major regression in regard to effectiveness with it, as its run value jumped up 13 in 2018, and saw a decline in whiff rate to 27.5 percent. Therefore, it is not surprising that 2018 was one of his worst seasons over his career, as his 5.30 xERA that year was a career high. It’s hard to find overall success on the mound when a pitcher has a pitch with that high of a run value.

In 2019 though, neither his slider nor four-seam fastball were good, as he posted run values of 2 and 5, respectively, which further explained his 5.27 xERA that season, only .03 points lower than his career. He did bump the whiff rate on his slider by 3.2 percentage points, but the whiff rate on his four-seamer decreased by nearly two percent. In 2020, he did find success again with the fastball on a run value (-3) and whiff rate (21.4 percent) basis, but his slider was a bit more mediocre, as the run value on the pitch increased to 4, though on a positive end, the whiff rate actually increased to 34.5 percent.

So what’s all this data mean? Well, one trend for Duffy is that one year his fastball production is solid, and the next year it’s mediocre. And the slider, for the most part, has been sub-par, especially since 2018.

But in 2021? Both the fastball and slider have been effective pitches for Duffy. His fastball is generating a run value of -4, and his slider is generating a run value of -2. Furthermore, the whiff rates have also increased by 5.4 percent and 3 percent on his fastball and slider, respectively, both impressive gains thus far. And lastly, he is posting plus-30 percent K rates on both pitches, which is extraordinary. Duffy hasn’t ever posted a K rate of 30 percent or higher on either pitch, let alone both, since 2017. Thus, it’s not surprising that Duffy has been so effective in his first three starts this year, posting an ERA 0.50, and xERA of 4.33, which would be his lowest xERA mark since 2017.

Granted, it’s just three starts, so it’s still early. However, if Duffy wants to continue this success and be a pitcher that hovers in the low-four or high-three’s in regard to ERA, his fastball and slider, and their effectiveness in terms of limiting runs, will be a huge factor in terms of making that happen.

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Increased velocity; decreased homers (But will that change with the weather?)

The biggest Achilles heel for Duffy, especially since 2018, has been the long ball. After only posting a HR/FB rate of 7.6 percent in 2017, Duffy saw his rates rise to 11.4 percent in 2018, 13 percent in 2019, and 13.7 percent in 2020. A big reason for those increases is that Duffy will often leave pitches in the sweet spot of the zone that can be easily driven for home runs.

The GIF below is an example of Duffy making a mistake in command to Christian Yelich of the Brewers, who makes him pay dearly:

So far this season, Duffy is not making as many mistakes in the zone, and even when he does, his increased velocity has helped make up for those errors. In 2019, his fastball velocity averaged 92.3 MPH. Last season during, the shortened season, his fastball averaged 92.2 MPH.

This year? His four-seamer is averaging 93.8 MPH, and it’s not just the increased velocity that’s making it more effective, but how he’s locating it.

Let’s take a look at Duffy’s contour heatmap on the fastball over the 2019-2020 seasons:

As one can see, the fastball is in the middle of the zone for the most part. Not necessarily bad if you are throwing upper 90’s. However, for a starting pitcher averaging 91-92 MPH? That’s “meatball” territory, and it’s not a surprise that opposing hitters posted such high HR/FB rates against Duffy over the past couple of years.

Now, let’s take a look at that four-seam fastball heatmap so far this year:

Duffy is elevating it a little bit more, as one can see him hitting with the consistency that upper middle part of the strike zone. He is also painting that left part edge of the strike zone as well, which is important, since that can be a tough zone to do much with. But pitchers live and die these days with their ability to elevate the high heat, and Duffy’s ability to not only locate his four-seamer up in the zone, but do so with much more velocity, is a big reason why Duffy has gotten off to such a sterling start in 2021.

In fact, let’s compare the difference a couple of MPH makes on that elevated fastball for Duffy. For example, in Duffy’s start against the Indians, he elevates a fastball against Josh Naylor in the same location as the Yelich at-bat in 2020. However, Duffy throws this pitch at 94.2 MPH rather than 91 MPH, like the one against the Brewers.

Take a look at the difference it makes:

That increased velocity on his four-seam fastball makes Naylor a little late on it. Thus, the result is simply a line out to Andrew Benintendi rather than a big fly to deep center, as was the case with Yelich. Furthermore, on more free-swinging hitters, even an elevated fastball out of the zone can be effective, as was the case on this strikeout against the Angels’ Jack Mayfield at Kauffman Stadium:

If that pitch is 91-92, like it has been in the previous couple of seasons, I’m not sure if hitters are chasing, especially in a 2-2 count with the bases loaded. But 94 MPH? That’s a lot faster and harder to lay off, especially in two-strike counts. Many Royals fans expected that a move to the bullpen would result in an increase in fastball velocity for Duffy. However, Duffy has increased the velocity in a starting role, and that has made him more effective overall this season.

That being said, one of the concerns for Duffy is that the exit velocity on batted balls against him has increased in 2021. Currently, Duffy is seeing an average exit velocity of 90 MPH on batted balls, which places him in the 39th percentile in that category, according to Baseball Savant. On a positive note, Duffy is doing a better job of limiting barrels this year, as his barrel rate is down from 7.5 last season to 6.3 percent, this year, which ranks him in the 63rd percentile. However, I do wonder if the early colder Spring weather, especially in Kansas City, has had an effect on limiting the impact of barreled balls and consequently, the HR/FB rates.

Now, Duffy typically profiles as a fly ball pitcher, as his career GB/FB ratio is 0.87 (anything over 1 tends to mean a pitcher is a ground ball pitcher; anything under 1 means they’re a fly ball pitcher). Thus, I wanted to see if fly balls hurt him more in the summer months (June, July and August, specifically), when the drier, hotter conditions made fly balls more likely to travel for home runs.

Here is the data I got from the past couple of seasons:

As you can see, his HR/FB rates were really high during those three-month periods during the last two years. Thus, it will be interesting to see if Duffy can neutralize that HR/FB rate like he has done thus far in 2021, or if those rates will spike once the weather changes.

Duffy has always been and continues to be a fly ball pitcher, so he’ll be susceptible to the home run, always. That being said, his ability to limit barrels this year has been a promising sign, and could go a long ways in regard to helping him decrease that HR/FB rate once the Royals hit the dog days of Summer.

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Does Duffy fit in the Royals plans after 2021?

With Salvador Perez signing an extension this off-season, Duffy becomes the big question mark for Dayton Moore this off-season, especially when looking at Royals payroll data via Roster Resource. Duffy is in a weird position as a free agent. He’s been the heart of this Royals franchise, along with Salvy, during this rebuilding era, but considering the Royals’ pitching depth in their farm system, it seems superfluous to keep him around. The Royals may be better off perhaps replacing him with one of their top arms such as Kris Bubic, Daniel Lynch, Jackson Kowar, or maybe Asa Lacy, depending on how Lacy progresses in the Minors this year.

That being said, the struggles of Brad Keller may make Duffy more important to keep around than initially imagined going into 2021. Keller’s issues with command and contact have really worked against him this season, as Keller is not only posting a career low strikeout rate (13 percent) and career high walk rate (13 percent), but he is also allowing a contact rate of 84.6 percent, which would be a career high, according to Fangraphs. Therefore, while this may be a bad stretch for Keller, and he may bounce back later in the year, the idea that Keller is a guaranteed long-term fit in the Royals rotation may have to be re-examined, especially if things don’t rectify for Keller in a major way in 2021.

Hence, what kind of deal should the Royals offer Duffy?

Honestly, I think it’s not out of the question to think that Duffy will get a two-year deal, similar to what the Royals offered Mike Minor, but maybe slightly less on an AAV end. Minor is making $7 million this year, $10 million next, and has a club option for $13 million in 2023 (with a $1 million buyout). Maybe Duffy doesn’t get exactly that, but perhaps instead of a roughly $9 million deal AAV-wise, what about a $6-7 million one over two seasons? It’s hard to imagine Duffy getting much more than that on the open market, and Duffy will be much closer to being “buried a Royal”, which he has said openly to the public.

There’s still a lot of baseball to be had in 2021, but right now, Moore may be wise to bring Duffy back on a modest 2-year, $12-13 million dollar deal for 2022 and 2023 (and hell, throw in a patented, extra $10-million club option on top of that for good measure). The troubles of Keller make Duffy more important as an asset, and Duffy is showing that he not only can provide leadership for the Royals during this turnaround, but he can also have an impact in the rotation as well.

Duffy will have to continue to put up solid numbers in 2021 of course…

But if he keeps this strong performance up, it’s going to be hard to imagine him in anything by Royals blue in 2022.

Photo Credit: Jamie Squire/Getty Images