Exploring Pitch Arsenal Changes

December 24, 2020

Jon Anderson explores starting pitchers who made changes to their pitch arsenal and selection in 2020 to determine whether these changes make them strong fantasy baseball values at SP.

It is really hard to know what to make of the 2020 season. This is especially true in the case of starting pitchers since the league leaders topped out around 80 innings pitched. As expected, there were many pitchers that posted much better seasons than expected, and many that posted seasons much worse. Given that the sample size is too small to inspire full confidence, we have to look a little deeper to make our judgments. You have likely heard the saying, "insanity is doing the same thing over and over again and expecting different results" before. This statement is commonly attributed to Albert Einstein, but it turns out he did not actually say it. It's unclear who did coin the phrase, so I'm going to jump in and just take the credit.

"Insanity is doing the same thing over and over again and expecting different results" - Jon Anderson

Whoever did say this first probably was not talking about fantasy baseball specifically, but it applies here nonetheless. A surprise breakout season is much less believable when it is not accompanied by a change. We should be more willing to buy into sudden improvements if something changed right before the good results started coming in. Our most obvious starting point then is pitch arsenal, meaning the distribution of the pitch types a pitcher threw. For this post, I have gone through and found every pitcher that threw 300 or more pitches in both 2019 and 2020, and then compared their usage of all of their pitches between the two seasons. Here are my most interesting findings in detail.

Corbin Burnes, Sinker/Cutter

After getting obliterated by the long-ball in 2019 (3.1 HR/9 in 49 innings), Burnes went back to the drawing board. The solution: abandon the pitch that gave up 13 of his 17 home runs: the four-seam fastball. He went from 52.5% usage of the pitch to 2.5%, a drastic change. Those pitches were replaced by sinkers (+30%) and cutters (+30%). Looking at the average launch angle for each pitch type (league-wide), it was a pretty good bet that this change would bring his home run rate down.

That bet paid off in a way that nobody could have expected. Burnes gave up just two home runs in his 59.2 innings in 2020 (a 0.30 HR/9). Last year, hitters made contact 80% of the time against the four-seamer and 86% of the time against the sinker (on swings). It would have made sense for Burnes to expect his strikeouts to drop a bit with this big change to his arsenal, but in actuality, they increased to a ridiculous 36.7% strikeout rate (up from 29.8%). All of this propelled Burnes to a true breakout fantasy season where he posted a 2.11 ERA and a 1.02 WHIP.

It's a little silly to project Burnes for another strikeout rate above 35% and a HR/9 rate below 0.5, but I don't expect him to have home run issues like 2019 ever again. The extent of the improvement he made in 2020 may have been a result of some luck, but I have very little doubt that Burnes will be a very viable fantasy starter in 2021. I think a strikeout rate above 30% is a safe bet as well as a ground-ball rate above 45%, which is a great foundation to build on.

Dinelson Lamet, Slider

In 2019, Lamet's main offering was a four-seamer (36%) and followed that with a curveball (32%). He completely overhauled his arsenal in 2020, throwing no curveballs and throwing his slider an astounding 53% of the time. He kept the four-seam usage about the same (37%) and filled out the rest of his distribution with sinkers. That made Lamet a three-pitch guy who threw sliders at a higher rate than any other starter in the league. The results were favorable, to say the least. He posted a 2.09 ERA with a 34.8% strikeout rate and even cut down on walks with a 7.5% walk rate. Lady luck played a part in that, as Lamet benefitted greatly from a .234 BABIP and a 7.9% HR/FB rate.

It is really rare to see a guy throwing this many sliders, but it is hard to imagine Lamet deviates a ton from that approach in 2021 given the success he had last year. Don't get me wrong, it's a great pitch (47.4% whiff rate in 2020, 51.3% in 2019), and he has a really strong fastball to back it up (average 97 miles per hour), but there is a reason this pitch distribution is so rare. Sliders and four-seamers are the most home run prone offerings in the game, and it is also more of a challenge to limit walks when you are throwing so few straight ones.

You can feel safe buying into Lamet's high strikeout rate again in 2021, but everything else feels primed for regression.

Justus Sheffield, Sinker

Sheffield struggled in his first real Major League stint in 2019, posting a 5.50 ERA while walking 10.7% of batters he faced. His main pitch was a four-seam fastball that season (47.8%), but in 2020 he completely stopped throwing that pitch and went to a sinker (47.4%). This led to a big improvement in walks (8.6%) but translated into a decrease in strikeouts as well (20.7%).

His success was mainly attributable to his ability to keep the ball in the yard (0.33 HR/9, 50.6% ground-ball rate). If a sinker continues to be his main pitch, he will likely stay above average in these categories, as that is a pitch that is hard to elevate for hitters. However, the strikeout rate is likely to stay low as well, making Sheffield a tough buy in the fantasy world. He does not have much in terms of velocity, which caps his upside, but we are talking about a guy who is just 24 years old here. We should not be writing Sheffield off as a guy who will never be a strong fantasy pitcher, but for right now the better bet seems to be to let someone else chase that strong 2020 ERA.

Shane Bieber, Cutter

In Bieber's breakout 2019 season, he was mainly a three-pitch guy (four-seamer, slider, curveball). In 2020 he introduced a cutter, which he threw a 16% clip. This added an element of surprise to his already phenomenal stuff and control, especially when facing left-handed batters. He did not like to throw his slider against lefties, so that left him without his best weapon against those hitters in 2019. Adding the cutter to the mix helped him become much harder to time up for those lefties, and the numbers show the massive improvement (lefties hit for a .194 wOBA against Bieber last year with a 40.1% strikeout rate).

While his overall numbers in the short-season are not repeatable over a full season sample, having another pitch does inspire even more confidence in Bieber continuing to deliver ace-level results.

Zach Eflin, Sinker

After a few years of mediocre results, Eflin decided to make a change in 2020 and become a true sinkerball pitcher. He threw this pitch 52% of the time. With sinkers, we expect high contact rates but also high ground-ball rates, it's a good tool for pitchers who want to pitch to contact and limit extra-base hits. Eflin did post a high ground-ball rate in 2020 (47.4%) but still gave up home runs at an average rate (1.22 HR/9). The strange thing is that his strikeout rate exploded up to 28%, up from an 18% rate in 2019. This happened with just a moderate improvement in contact rate (dropping from 81% to 79%).

This is all to say that you should not believe Eflin is now a high strikeout pitcher because nothing backs it up. He may continue to be better than he was in 2017-2019, but there is almost no chance he ever strikes out hitters at a rate above 25% again. You should be expecting a lot of contact and a lot of groundballs, but not nearly enough strikeouts to be a good option for your fantasy team. Ignore 2020 in this case and fade Eflin in your drafts.

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