Brad Keller Remains a Solid Starting Option for Royals Despite Rough Recent Starts

Brad Keller continues to be an enigma for Matt Quatraro and the Royals coaching staff.

The 27-year-old Rule 5 Draft pick is coming off two rough seasons in which he posted a 5.39 ERA in 2021 and a 5.09 ERA in 2022. Over the last two years in Kansas City, he has produced a combined 1.8 fWAR in 61 appearances and 273.1 innings pitched since the 2021 season.

That is especially disappointing since Keller had a career-best campaign during the COVID-shortened 2020 season in which he produced a 2.47 ERA and 1.3 fWAR in nine starts and 54.2 IP. His strong 2020 season had many Royals fans thinking that he could’ve been an extension candidate prior to the 2021 season.

Thankfully for the Royals, no extension was made, and Keller is in his final season of team control before becoming an unrestricted free agent next winter.

Needing a solid campaign this year to either prove himself to the Royals or any free agent suitor next offseason, Keller has adjusted to new pitching coach Brian Sweeney and the pitching coaching team, which also includes assistant pitching coach Zach Bove.

Keller’s most recent adjustment this past spring was to add a curveball to his repertoire, and he has not been shy to throw the pitch in games this season.

Keller is currently throwing the curveball 26 percent of the time, which is his second-most thrown pitch in 2023, behind only his four-seamer (31.8 percent usage). Though he didn’t throw his curve a lot in his last start against Arizona, the curve has been a pitch he has heavily relied on in most of his outings this year, as evidenced in his by-game pitch percentage chart this season, via Savant.

For the most part this season, Keller has not given up a whole lot of hits or runs in his first five outings.

His ERA is respectable at 3.96, as his xERA, which is 4.11. Furthermore, his 0.36 HR/9 and 6.5 H/9 are his lowest rates in those categories since 2020, when they were 0.33 and 6.4, respectively.

And even though the average exit velocity on batted balls off of Keller is up at 90.4 MPH this season (1.1 MPH higher than 2022), his barrel rate is down to 4.5 percent and his launch angle on batted balls allowed is also down at 3.9 degrees. Even when Keller gives up hard contact so far against opposing hitters this year, it hasn’t done too much damage in the grand scheme of things.

That said, his last start against the Diamondbacks could be a cause for concern for Royals fans.

Keller not only went just four innings, but he also allowed four hits, and four runs, and gave a career-high six walks in the Royals’ 5-4 loss on Monday. Additionally, he also struggled with his curveball command and control, as it generated a CSW rate of zero, which can be seen in the exit velocity and strike data below, via Savant.

Over his last two starts against the Diamondbacks and Rangers, Keller has given up seven runs in eight innings of work as well as 11 walks. That is a far cry from the four runs and eight walks allowed in 18 innings of work in his first three starts of the 2023 season.

And thus, is Keller pitching his way out of the rotation, even with the Royals’ need for starting pitching in the wake of Kris Bubic’s injury? Or are the past two starts just a blip on the radar that Keller can bounce back from, especially once he regains his feel and command on his curveball?

Let’s take a deeper dive into what Keller has produced so far in 2023, and what Royals can expect from him going forward for the remainder of the season, if healthy.

His Start to 2023 Fueled by His Breaking Pitches

Over the past two years, Keller’s primary pitch was his slider, which he threw 34.8 percent and 36.2 percent of the time in 2021 and 2022, respectively.

However, that has changed dramatically with the addition of the curveball, as Royals fans can see below in his pitch percentage chart by year, via Savant.

Keller is only throwing the slider 15.3 percent of the time this year, which is a 20.9 percent drop from the previous year. Considering the curveball is a newly-added pitch though, it’s not a surprise that the slider has seen such a drop this year, especially since it was the only breaking pitch in his repertoire prior to 2023.

What’s interesting to note is that the introduction of the curveball and the decreased usage of the slider has actually made both of those breaking pitches his most effective this year on a pitch quality end. Royals fans can see that in the PLV pitch quality charts below, via Pitcher List.

While the four-seamer and sinker remain below average (five being average on a PLV end), the curveball and slider have been able to be above-average offerings on a PLV end for Keller. And this is despite his last start against Arizona when his curveball PLV was downright awful, which can be seen in the game table below:

His curveball had a PLV of 4.36 against the Diamondbacks, which was the worst mark of the five pitches he threw on Monday. In addition, it only had a quality pitch percentage (QP%) of 25 percent and a bad pitch percentage (BP%) of 50 percent, which expectedly produced a woeful -25 Q-BP% for the game.

Based on the location of his pitch, via Savant Illustrator, it shouldn’t be alarming that Keller’s curveball produced such woeful results in his most recent outing.

His slider wasn’t as bad as the curveball against Arizona, but it didn’t necessarily produce a whole lot of positive results either.

Not only did it have a 4.85 PLV for the game, but it also only sported a QP% of 38.9 percent and broke even on a Q-BP% end as well. Furthermore, his curve and slider had the highest PLA marks for the game at 8.00 and 5.94, respectively (PLA is PLV converted as an ERA metric, kind of like FIP).

On the other hand, let’s take a look at what the PLV data looks like when Keller has his feel and command of his breaking pitches, which was the case in his April 12th start against the Rangers, which was a 10-1 Royals win.

In his April 12th start against the Rangers, he posted a PLV of 5.85 and PLA of 1.17 on the curve, and a 5.96 PLV and 0.85 PLA. That is in addition to a 63 percent QP% and 75 percent QP% on the slider.

As a result, notice how the CSW and hard contact results were not just better for the pitches, but his repertoire as a whole against the Rangers in that particular start.

Not only did Keller produce an overall CSW rate of 29.5 percent, but he also maintained a hard-contact rate of 24 percent over 105 pitches.

That’s a big reason why a normally prodigious Rangers lineup was only held to three hits and one run by Keller.

Keller’s Curveball Command

In his rough outing against the Diamondbacks, we saw Keller constantly lose command on the arm side area of the strike zone with the curveball.

On the other hand, let’s take a look at what the strike zone plot for the curveball looks like from his April 12th start against the Rangers.

Notice how much more Keller “raids the zone” with the curve against Texas in comparison to his start against Arizona. What’s interesting to note is that throwing more curves in the strike zone against the Rangers led to more chases on the pitch as well.

Against Texas, Keller had an O-Swing percentage of 46.2 percent which heavily contributed to his 44.4 percent CSW rate generated on the curve on April 12th. On the flip side, his curveball O-Swing against the Diamondbacks was only 9.1 percent, which also correlates with his zero percent CSW rate on the pitch.

The more Keller can throw the curve in the strike zone, the more successful he will be overall. And this is not just with called strikes in the zone, but on chases out of the zone as well.

Unfortunately, he is trending in the wrong direction in both areas recently.

His in-zone percentage with the curve is trending down in his last few starts, and likewise, his chase rate is also following a similar pattern, as Royals fans can see in the chart comparison via Savant.

When Keller is hitting that lower part of the strike zone with the curve, the pitch has proven to induce chases when it is thrown out of the strike zone this season. That was the case against San Francisco on April 7th, when he produced a CSW rate of 34.8 percent and an O-Swing percentage of 62.7 with the curveball against Giants hitters.

Here’s a GIF sequence from that outing of a called strike in the zone against Lamonte Wade, Jr. and chase out of the strike zone on the curve by Blake Sabol.

Sabol and other Giants hitters wouldn’t be chasing that curve if Keller wasn’t establishing the curve in the strike zone like he did against Wade in his at-bat.

The bottom line?

In order for Keller to find success again with the curveball (and on a more consistent basis throughout 2023), he has to be able to locate it in the strike zone again on a consistent basis, much like he did against San Francisco and in his first start against Texas this season.

The Outlook on Keller

At this point, I do not think Keller is in danger of losing his rotation spot anytime soon.

The Royals do not have a whole lot of reserves pitching well in Omaha right now, as Max Castillo, Jonathan Heasley, and Jackson Kowar, starting pitcher options on the 40-man roster in Triple-A, haven’t pitched well.

Alec Marsh, who also is on the 40-man roster, has gotten off to a good start in a repeat of Double-A Northwest Arkansas. However, it feels like he may still be a couple of months away at the soonest before he gets an opportunity at the big league level. Nonetheless, his start should not be ignored, especially considering how rough his 2021 was.

What has been an interesting trend for Keller is that he is keeping the barrels and home runs down, which is something that he has struggled with before in the past.

Last year, he allowed a HR/9 of 1.10 and in 2021 it was even worse at 1.21. While that number is bound to go up a bit this year due to regression, if he can keep his HR/9 under one, like he did in 2019, it is possible that Keller could have a season like 2019 when he produced an ERA of 4.19 and fWAR of 2.2, according to Fangraphs.

That said, Keller has struggled with the ball flying when the weather has heated up. Over the past two years, he has seen HR/9 spikes in May, June, and August, which has had an overall effect on his FIP, based on Fangraphs data.

In order for Keller to not repeat what he did in May, June, and August of 2021 and 2022, limiting the long ball will be key. To do that, it will be important for him to limit the barrels on his four-seamer.

When Keller particularly struggled in 2021, it was due to the 16 percent barrel rate on four-seamers that season. He was able to see some regression last year in his four-seamer barrel rate, as it was only 6.1 percent, which was a positive development, despite the uneven 2022 campaign for him personally.

Unfortunately, that four-seam barrel rate has jumped up a bit so far to begin the year, which can be seen in the barrel rate chart below:

The good thing for Keller in the case this year is that even though they’re barreling the ball, the average launch angle on batted four-seamers remains low at three degrees. That is not only better than the 14-degree launch angle in 2021 and the six-degree average launch angle in 2022.

Interestingly enough, the only home run Keller has allowed on the four-seamer was on a pitch way up and out of the strike zone to Texas’ Nate Lowe. It wasn’t really a bad pitch location-wise, but simply a great swing by a great power hitter like Lowe.

Nonetheless, how balls fly off the bat during the summer months, especially against the four-seamer, could be a big indicator of whether or not Keller truly takes the next step under this new coaching staff or continues to be the same pitcher that he’s been over the past two years.

Royals fans in May and June should be paying attention to Keller’s curveball command and the batted-ball quality off of his four-seamers.

Those are the two developments in the next couple of months that could determine whether the Royals extend Keller at the end of the year or perhaps let him go via free agency (or DFA him mid-year if things really go south).

At this point, it still could go either way, but if Keller wants the former to happen, he’s going to need to show improvement in those two areas in May.

Photo Credit: LM Otero/AP


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