Can Brad Keller prove that 2021 was a fluke? (“Bounce Back Royals” series)

Opening Day should have been an omen for Royals fans in regard to Brad Keller and what his 2021 season would be like.

After posting 2.47 ERA and accumulating a 1.3 fWAR in nine starts and 54.2 IP during the shortened 2020 season, Keller was an absolute disaster on Opening Day at Kauffman Stadium against the Texas Rangers. In 1.1 innings of work, Keller allowed nine hits, three walks, and six earned runs while striking out zero on 51 pitches. Granted, Keller didn’t allow a home run, and he only allowed four “hard-hit” balls, according to Baseball Savant, which was actually half the number of hard-hit balls allowed by Rangers reliever Taylor Hearn in 2.1 IP. However, it was a sign that after years of getting lucky, the 2021 season was going to be a different story for Keller in the Royals rotation.

And if anything, this double by Nate Lowe in the top of the first inning on April 1st basically encompasses Keller’s struggles last year in one tough-to-watch clip:

Sure, Keller left it a little up in the zone, and Lowe did what he needed to on it by going the opposite way. But he threw his four-seamer at 95 MPH, which was actually two MPH faster than what he threw on the four-seamer in 2020. Also, he was done in by a bad judgment by Andrew Benintendi in left field, who eventually overcame his early-season follies in the outfield to earn his first Gold Glove award in his first season in Kansas City:

That being said, one can only judge a player by what “actually” happens on the field or on the mound.

And in 2021, Keller was a pitcher who put up a 5.39 ERA and only accumulated a 1.1 fWAR in 26 starts and 133.2 innings of work as the Royals’ “number one” starter.

Not only was Keller’s campaign a major regression from 2020, but it was his worst season at the Major League level on an ERA, FIP, and fWAR end, which was disappointing considering the gains Keller made in Kansas City after being acquired in the Rule 5 Draft in 2017. Furthermore, add in the fact that Keller was shut down in September due to forearm issues, and Royals fans have to wonder what his future will be like in Kansas City, especially as he enters his second year of arbitration.

The Royals do not necessarily need Keller to be a No.1 starter in 2022. With Daniel Lynch, Brady Singer, Kris Bubic, Carlos Hernandez, and Jackson Kowar all expected to compete for spots in the rotation with Keller and veteran Mike Minor, even being a decent end-of-the-rotation arm would be a huge boost for this Royals pitching staff. However, can Keller bounce back after a disappointing season? Or is Keller closer to what he showed in 2021, which is a pitcher who may not necessarily be a starter who can go out and succeed consistently throughout the long 162-game season?

If the Royals want to be a winning club, the Royals will need an effective Keller, whether it’s in the rotation or long relief…


Now, when it comes to finding Keller’s positives from 2021, Royals fans won’t find it in his traditional or surface-level metrics. Keller’s 6.52 xERA was a career-worst, and ranked him in the bottom 1st percentile in baseball in that category, according to Baseball Savant. In fact, when looking at his 2021 percentiles from Baseball Savant, there are a lot of percentiles in the light to dark blue, which is not a positive sign for a pitcher, let alone one who was the Opening Day starter for the Royals last year.

As Royals fans can see above, there were six categories where Keller ranked lower than the bottom 10 percentile in baseball. He also ranked in the bottom 22nd percentile in four categories, 20th percentile in whiff rate, and 13th percentile in chase rate. Hence, it is not a surprise that Keller put up a career-worst xERA, but also a career-worst in many other metrics such as ERA, FIP, and xFIP as well.

Granted, what Keller did last year when looking deeper into his profile, isn’t all that different from previous seasons, especially in certain metric categories.

For example, while his xERA and xBA ranked in the bottom first and third percentiles, respectively, they both ranked in the 44th percentile back in 2020, which is better, but still in that “lower-than-average” area. He also ranked in the 33rd percentile in average exit velocity on batted balls in 2020, which was only 11 spots better than 2021. And his hard-hit rate allowed, which ranked in the ninth percentile this past season? Well, that ranked in the 37th percentile in 2020 and the 31st percentile in 2019.

Therefore, I am not necessarily sure that Keller was that much worse of a pitcher in 2021 than he was in 2020 and even 2019.

In fact, Royals fans could point to regression simply hitting Keller hard in 2021, especially when one looks at his BABIP from last season, which is demonstrated in the Fangraphs chart below:

Notice how for two straight seasons, Keller was vastly below league average in terms of BABIP. Then last season, his BABIP was nearly 50 points higher than the league average, which explains why Keller’s FIP (4.72) was lower than his ERA (5.39) for the first time in his career. This wild difference in 2021 from his career trends was also evident in his strand rate (LOB%), which also typically correlates with “luck” for pitchers.

Take a look at Keller’s strand rates from 2021, and how it nosedived from 2020 (and how below league average is as well):

Now, Royals fans can’t blame Keller’s rough 2021 solely on “bad luck” regression. Keller did allow a career-high HR/FB rate (14.9 percent), and after showing an elite ability to avoid barrels in the first three seasons of his career (he ranked in the 89th percentile in 2020), he saw his barrel rate balloon to 10.9 percent, which placed him in the bottom ninth percentile last season, according to Savant.

So, while Keller would benefit from some BABIP and LOB percentage correction, he will need to command his pitches better if he wants to return to that 2019 and 2020 form.

And a lot will depend on his command and control of his four-seam fastball, which went through some tremendous ups and downs during the 2021 season.


What’s interesting about Keller’s four-seamer was that he saw some gains on the pitch in a couple of categories. His four-seamer averaged 94.2 MPH, which was actually 1.8 MPH faster than 2020. Furthermore, Keller’s four-seamer generated a whiff rate of 22.5 percent, and a K rate of 19.2 percent, which was not only better than what he produced in those categories in 2020 (11.1 percent and 14.5 percent, respectively) but 2019 as well (18.1 percent and 17.1 percent, respectively).

However, while Keller produced a run value of -3 on the four-seamer in 2020, and 0 in 2019, his run value ballooned to 18 in 2021, which was easily the WORST pitch from his four-pitch repertoire last season. Considering his four-seamer was his second-most thrown pitch last year at 29.8 percent, he will need to see some improvement in command in 2022 if he wants to see some positive results on the pitch next season.

When it comes to hits allowed, it’s interesting to see where hitters thrived against Keller’s four-seam fastball. I decided to take a look at heatmaps of Keller’s four-seam fastballs that resulted in base hits from not just last year, but the 2019-2020 season combined as well.

Here’s what Keller’s heatmap from 2021 looked like:

And here is what his heatmap from the combined 2019-2020 season looked like, comparatively:

When it came to hits allowed, in 2021, hitters seemed to thrive on that inside edge to left-handed hitters (or outside edge to right-handed hitters). When it came to hits allowed on the four-seam fastball in 2019 and 2020, hitters took advantage of pitches thrown right down the middle by Keller. The latter makes sense. Fastballs thrown right down the middle will get hit hard, especially considering Keller’s fastball averaged 92.8 MPH in 2020 and 93.7 MPH in 2019.

However, I found it surprising that Keller was getting hit in ONE specific edge of the strike zone, especially with his velocity up from previous years, which should theoretically, with both of those factors in play, make it harder for batters to hit the pitch. So I took a deeper look into Keller’s Statcast game logs and tried to find pitches that would have been in that “red spot” on the heatmap chart.

Here’s an example of St. Louis’ Paul DeJong going the opposite field for a double on an 0-2 count:

And here’s a pitch in the same zone in a two-strike count against the Yankees’ Luke Voit, who takes it to the opposite field for a home run over Yankee Stadium’s short right-field porch:

Notice how both pitches came on two-strike counts and were located in hittable parts of the strike zone. Keller did see an increase in chase rate this past year, as it improved from 23 percent in 2020 to 24.4 percent in 2021. Furthermore, Keller also saw some improvement in his CSW rate (called strike plus whiff rate), as it too went from 24.8 percent in 2020 to 25.4 percent in 2021, which was a career-high. So Keller did get better at getting batters to chase and swing and miss last season.

However, he made too many mistakes in one part of the strike zone with his four-seamer a year ago, and hitters made him pay dearly for it. He will need to minimize those mistakes with his fastball if he wants to rebound on the mound in 2022.


While Keller did see an increase in strikeout rate (16.3 percent in 2020 to 19.6 percent last year), he did post a career high walk rate at 10.4 percent. This resulted in him having a K/BB ratio of 1.88, which was the second-lowest of his career (his lowest came in 2019, when it was 1.74).

A big area of struggle for Keller, which has been a recurring problem, has been his ability to be productive in the “chase” zone of the strike zone.

Take a look at how high his run value was in the chase zone from his Statcast Swing Take data via Baseball Savant:

As Royals fans can see from the chart above, Keller was +23 runs in that yellow chase zone, and that is mostly due to hitters not chasing Keller’s pitches outside the strike zone. Notice in the far right under the Run-Value graph, Keller gave up 35 take runs, while only generating -11 swing runs (remember, plus is bad). Keller has traditionally been below league average in chase rate (24.4 percent last year; 28.3 percent league average) as well as edge percentage, which measures how often Keller gets calls on the edges of the strike zone (41.1 percent last year; 42.6 percent league average). Therefore, it’s not surprising that Keller struggled in this area not only last year but also two seasons ago.

Take a look at his 2019 Swing Take data chart via Savant:

Notice how Keller was still pretty bad in the chase zone two years ago, as he was only five runs better than 2021. That being said, Keller was really good in the heart of the zone, as he generated -12 swing AND take runs. Keller displayed much better command in the heart of the zone in 2019, and if Keller wants to be that kind of pitcher, he needs to see either some minor gains in the chase zone (which may be hard to ask for at this point in his career) or he needs to get back to succeeding in the heart zone again like he did two years ago.

Keller’s command will be the key to his rebound in 2022. The increase in strikeouts was promising, but the corresponding rise in walks suppressed any good feelings that came from the increase in four-seam velocity and strikeouts. Keller changed his approach last year as he threw his slider more than ever, as it was his primary pitch last season with a usage rate of 34.8 percent. Keller’s slider has been his best pitch over his career, as it has consistently generated positive run value, even with the increase in usage, as evidenced by this data below:

Over the past three seasons, Keller has accumulated -25 runs on his slider, and it’s easy to think that the pitch can be sustainable going forward. When Keller commands the slider effectively, it was an effective strikeout pitch, as he generated a K rate of 30.7 percent on the pitch, the highest K rate of any of his four pitches a season ago.

Here’s an example of Keller locating the slider effectively in the lower chase zone, which results in Keller striking out Brian Goodwin of the White Sox at Kauffman Stadium in a game in late July:

So, there are some areas for Royals fans to be encouraged about when it comes to Keller’s outlook in 2022. An increase in velocity is a good thing. More strikeouts with his primary pitch (slider) is a good thing. An increase in strikeouts and CSW rate is a good thing. The fact that his BABIP and LOB rate was so ridiculously different from the previous year “should” be a good thing going forward (after all, it can’t be that high again, typically).

But then again, there are some major concerns as well. An increase in walks and home run rate is a bad thing. His struggles to command his four-seam fastball is a bad thing. His inability to be effective in that chase zone, and seeing a major regression in the heart of the strike zone is a bad thing.

Thus, it comes down to one thing, ultimately: will Keller leverage the good he showed in 2022, or will the bad continue to manifest itself when Keller is on the mound next season?

Whichever happens could not only determine Keller’s performance next season, but also his future as a Royal, as he will be a free agent after the 2023 season.

Granted, the Royals have a lot of options in the rotation in the future, especially with the addition of Jonathan Bowlan to the 40-man roster, who could breakout in 2022 after missing most of the year due to injury. And thus, Royals fans have to wonder if Moore and JJ Picollo will get creative with Keller, especially considering his inconsistency this past year. Would Keller perform better in a relief role over a limited number of innings? Would that be a better fit for him in 2022, and preserve his future after next season with the Royals?

Keller’s future is an interesting one, mostly because last year couldn’t have gone much worse for him, especially since there was some discussion that Keller maybe merited an extension prior to the 2021 season.

Whatever Keller’s future is in Kansas City, whether it’s in the rotation or bullpen, this much is certain: the Royals will need a Keller who is closer to his 2020 and 2019 self rather than the pitcher he was last season if they want to be competitive in the AL Central in 2022.

A healthy and productive Keller could provide the stability this Royals pitching staff needs, and perhaps take the pressure off their young starters, who may still go through some growing pains as they continue to adjust to Major League hitters.

Keller’s 2021 wasn’t a total lost cause. There were some positives to be had, and the data I talked about in this post demonstrates that.

But there were a lot of discouraging things as well, and it will be important that he works and improves upon those negatives this Spring Training if he wants to rebound on the mound next season.

Photo Credit: Ed Zurga/Getty Images

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