Last season was a year to forget for Royals starting pitcher Brad Keller.

After posting a career-best 2.47 ERA in nine starts and 54.2 IP in the shortened 2020 season, Keller entered 2021 as the Royals’ Opening Day starter, with hopes that he would continue to be at the top of the Royals rotation for years to come.

Unfortunately for Keller, expectations for him plummeted immediately, as Keller’s rough Opening Day start against the lowly Texas Rangers (nine hits, six runs in 1.1 IP) proved to be a sign of things to come for the upcoming season.

For the year, Keller posted a 5.39 ERA and 1.66 WHIP in 26 starts and 133.2 innings pitched. It was not only the worst season of his career since debuting with the Royals in 2018, but it was also the kind of campaign that made Royals fans question what Keller’s long-term outlook may be in Kansas City.

Going into the 2021 season, there were rumblings that Keller could receive an extension, especially since he will be a free agent after the 2023 season.

However, after his debacle in 2021, the main question about Keller now is if he will stay in the starting rotation? Or will he will eventually make a move back to the bullpen, which is where he started when he first debuted with the Royals back in 2018?

The Royals do not have to make such a rash decision so quickly, especially with so many of the young arms in the Royals system still unproven. Keller will most likely start the year in the Royals starting rotation, and there is a strong possibility that he could make a second-straight Opening Day start, should he bounce back with a solid Cactus League campaign in 2022.

After all, Keller did perform better on the mound in the months of May and July, and his second-half numbers were more palatable than his first-half metrics, as seen in the table below:

Keller’s overall year wasn’t pretty by any stretch of the imagination. However, when looked at closely and on a month-by-month basis, there were some signs that Keller was getting out of his funk, and that could have possibly been realized more down the stretch, had he not been shut down at the end of the year due to precautionary reasons.

On the other hand, if Keller wants to get back to that 2018-2020 self (which was a pretty decent, if not good, pitcher), then he will need to address the issues with his two fastballs from a season ago: his four-seamer and sinker.

---

Keller and His Four-Seamer

When looking at run value data of pitches Royals pitchers threw in 2021 via Baseball Savant, Keller’s four-seamer was the worst pitch thrown by any Royals pitchers and by a considerable margin.

Here’s a look at the 10 worst pitches thrown by Royals pitchers on a run value end, and notice Keller firmly entrenched up at the top of the list.

Now, on a run-value per 100 pitches end, Keller’s four-seamer (2.5) wasn’t as bad as Jackson Kowar’s changeup (5.5) or Daniel Lynch’s changeup (3.9). That being said, it was still the third-worst pitch thrown by Royals pitchers on that metric, which is not a badge of honor by any means.

What’s interesting to note is that at the surface level, there were some improvements on Keller’s four-seamer in a couple of categories.

First off, Keller’s four-seamer averaged 94.2 MPH last year, a 1.4 MPH improvement from his mark in 2020. Furthermore, Keller’s four-seam fastball also generated a whiff rate of 22.5 percent, a K rate of 19.2 percent, and a put-away percentage of 17.5 percent. Those were career-bests for him in those categories in regard to the four-seamer.

And he did this despite throwing the pitch only 29.8 percent of the time, a career-low.

When Keller commanded the four-seamer effectively in 2021, it produced some good results, especially on a swing-and-miss end. Here’s a look at Keller’s heatmap from last season on swinging strikes he generated from the four-seamer:

And here’s an example of Keller pumping the four-seamer at 95 MPH in that red dot area from the chart above against Tampa Bay’s Austin Meadows back in May:

So, there are some positives to be had from his four-seamer. However, why did his four-seamer rate so poorly on a run value end in 2021?

Well, when he DIDN’T command it, hitters feasted on it. That is evidenced in the batting average and slugging percentage data on the pitch, which comes courtesy of Savant:

As Royals fans can see, Keller’s four-seamer experienced a career-high on a batting average and slugging end last year. Additionally, the four-seamer was 146 points higher on a batting average end, and 241 points higher on a slugging percentage end from 2020. Those are significant jumps, and a big reason why Keller’s four-seamer saw a 20 run swing in run value from 2020 to 2021.

On a wOBA basis, the four-seamer also saw a tremendous spike up in 2021 after a tremendous spike down in 2020.

Based on that graph above, some regression on the pitch was to be expected from Keller in 2021, especially since the four-seamer only had around a .242 wOBA in 2020, which was nearly 100 points lower than his mark in that category in 2019.

However, even on an expected wOBA end, the spike was still evident last season, which further demonstrates how ineffective Keller was with his four-seamer in 2021.

A big contributor to these spikes in run value, wOBA, and xwOBA from 2020 to 2021 on his four-seamer could be credited to the fact that hitters were able to connect on the four-seamer more than ever before, as well as more productively to boot.

Not only did hitters improve on average launch angle on the four-seamer by a significant margin (3 degrees in 2020 to 14 degrees in 2021), but the barrel rate on his four-seamer also saw a career-high, as evidenced in the graph below:

Notice how the barrel rate on four-seam fastballs is nearly double the rate of his previous career-high in 2019.

That is NOT an encouraging trend.

Let’s take a look at where hitters did the most damage against Keller when he threw his four-seam fastballs in the wOBA zone chart below:

When Keller threw his four-seamer up in the zone, he pretty much had success (and his whiff heatmap backs this up). However, pretty much anywhere else in the strike zone, especially in those middle parts of the zone, his four-seamer got rocked.

Granted, four-seamers thrown in the middle of the zone, especially without a lot of rising movement, will tend to get mashed. But last year was particularly bad, especially when Royals fans take a look at Keller’s same chart from two seasons ago:

Notice the upper glove side area of the strike zone in both charts. There is a 299 point difference from 2020 to 2021, which is huge. Furthermore, here’s an example of Keller throwing it in that zone a season ago, and it getting barreled the opposite way at Yankee Stadium by Luke Voit:

it is likely that his four-seamer won’t be as bad in this upcoming season as it was in 2021, especially if Keller’s history with the pitch in 2018 and 2019 is any indication.

However, his usage rate with the four-seamer was a career-low in 2021, and considering the struggles he had, it isn’t out of the question to think that his four-seamer usage will continue to drop in 2022.

---

Keller and His Sinker

An interesting trend note from 2021 was that while Keller’s four-seam fastball usage was a career-low, his sinker usage spiked to a career-high.

On an annual basis since 2018, his four-seamer and sinker usage have correlated with one another (the four-seamer going down with the sinker going up) based on the pitch usage chart via Savant:

On a whiff and strikeout end, the sinker is not as effective a pitch as the four-seamer. That is evident when comparing the whiff, strikeout, and put away rate metrics on the two pitches, demonstrated in the table below:

However, the sinker was a much better pitch at generating groundballs than the four-seamer in 2021.

Here is the batted ball data on his sinker, which comes via his Pitcher List player profile (a benefit of the PL 7.0 upgrade):

Now, let’s compare what that batted ball data looks for his four-seamer:

As Royals fans can see, Keller was nearly 20 percent better at generating balls on the ground with his sinker, in comparison to his four-seamer.

That’s why the sinker proved to be an effective weapon to get out of jams, even though the pitch paled to the four-seamer in whiff rate (11.6 to the four-seamer’s 22.5 percent) and strikeout rate (7.4 percent to the four-seamer’s 19.2 percent).

Here’s an example of Keller utilizing his sinker effectively against Chicago’s Yoán Moncada to induce a groundball to shortstop Nicky Lopez that results in a double play to end the inning at Kauffman Stadium:

Keller certainly still had issues with command of the sinker last season. Keller’s sinker still produced a wOBA of .393, which was only eight points lower than the four-seamer. Furthermore, his run value of seven on the pitch was tied for the ninth-worst pitch from Royals pitchers last year on a run-value end.

So, while his sinker was better than his four-seamer, it wasn’t a “great” pitch either by any stretch of the imagination.

And a big reason for that was due to the home run issues Keller had when he threw the sinker.

Royals fans may have noticed already in the batted ball charts above, but his HR/FB rate of 26.9 percent on the sinker was 11.3 percent higher than the HR/FB rate on the four-seamer. When Keller located the sinker low in the zone (like in the GIF above), he was able to generate groundball outs effectively.

However, when he located it up in the zone, it produced home runs like this bomb by Patrick Wisdom at Wrigley Field in August:

There’s no question that Keller’s sinker could be an effective complement to or even substitute for the four-seamer. The sinker’s ability, when commanded well, to generate groundballs is amplified with the Royals’ plus infield defense behind Keller.

That being said, Keller needs to harness his command on the pitch if he wants to use it more in 2022, as it resulted in more long balls than four-seamer a season ago.

---

Final Thoughts

Keller was able to channel his slider effectively in 2021, as he not only threw it the most of any pitch in 2021 (34.8 percent), but it was also his most effective pitch on a run value end (-3).

And yet, if he wants to enhance the slider and be more effective overall in 2022, he will need to rebound with his fastballs, and focus on either the four-seamer or sinker more solely to find success.

Does Keller want to continue to grow as a strikeout pitcher, which did happen last year (his 19.6 K percentage was a career-high)? If that’s the case, he may want to rely on utilizing the four-seamer with more regularity in 2022.

Or does Keller want to revert to being more of a groundball pitcher who takes advantage of Lopez, Adalberto Mondesi, Whit Merrifield, and perhaps Bobby Witt, Jr., behind him? Should he decide to go that route, the usage difference between the sinker and four-seamer could be even greater in favor of the former pitch next season.

Whatever Keller chooses to do, he will need to pick a path and make the proper adjustments this Spring, especially if he wants to stay in the Royals’ starting rotation long-term.

Because plain and simple, he can’t afford to have another season like 2021…

Especially with all the pitching depth in the Royals system ready to take the next step in 2022.

Photo Credit: Abbie Parr/Getty Images