RADIO
There are two ways for a pitcher to get a hitter out:
- Strike them out
- Generate a ball in play that can be handled for an out
We talk a ton about strikeout and walk rates here, as we should - those stats are the best predictors of success in baseball. But they don't tell the whole tale.
Since 2015, we have been able to better measure the quality of contact with Baseball Savant. We get a ton of information about each batted ball. This has helped us immensely in projecting hitters. We also talk a lot about the quality of contact allowed by pitchers. This is obviously something of great importance, since most of the time a plate appearance is ending with a ball put up in play, and the quality of the contact determines a lot of what happens with a pitcher's end-year stats.
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In this post, I wanted to explore the statistic of expected weighted on-base average on contact (xwOBACON) allowed. Here's what I have come up with:
What Is it?
Here is how this thing works, basically:
- For each batted ball, the launch angle and launch velocity are taken.
- The system uses the history of similar batted balls to determine what the most likely outcome of that type of batted ball is.
- It assigned a wOBA number to the batted ball event based on that history.
The most well-hit batted balls get an xwOBA figure of around 2.0. A ball that will go for an out nearly every time will fall really close to a 0. xwOBACON takes all of the batted balls and averages out those numbers.
The best mark of the last five seasons (not counting 2020) among qualified SPs was Corbin Burnes in 2021, who allowed just a .304 xwOBACON. The worst mark was Tarik Skubal's 2021 season where he allowed a .454 mark. The average is around .360-.365.
Is It Sticky?
What we are asking with this question is "if a guy excels in this one year, is it smart to predict that he will do so the next year?"
Strikeout-to-walk ratio (K-BB%) turns out to be a very sticky stat. This is largely skill-based, so a good pitcher will put up a good number almost every year and a bad pitcher will put up a bad number. The correlation between K-BB% in year N and the K-BB% in year N+1 is 0.82 - a strong positive relationship. Here's a look at all the pitchers with a K-BB% above 20% in 2021 and what they did in 2022:
The average K-BB% there in the 2022 column was 21.1% - an elite number. Almost all of the pitchers here posted a very strong number the following year as well - although we aren't without exceptions (Gilbert, Berrios, Webb, Giolito).
For xwOBACON, it's just not the same story. The correlation is 0.29 between qualified pitchers' xwOBACONs in 2021 and 2022. 2021 did not predict 2022 well at all.
Here's the same kind of table. I took all the pitchers in 2021 that put up marks below .350 and brought in their 2022 mark:
We still see most of the numbers in 2022 being below average, but we see plenty of jumps in either direction. Burnes could not replicate anything close to that .299 mark, Sandy Alcantara improved massively, and Kyle Gibson fell apart. This is a small number of pitchers we're showing here, but the trend of near randomness remains no matter what you're looking at - this statistic is not a true skill - there is a lot of randomness that goes into it.
That doesn't mean Corbin Burnes has any real chance of seeing a .400 xwOBACON in 2023. His pitches are tough to hit, so even when a hitter does make contact - it's going to be weak contact a lot more often than say Patrick Corbin. The point here is to say that it is not at all uncommon to see big shifts in this stat for an individual pitcher year-to-year.
The Outliers
I'm not a total egghead. I realize that there are some pitchers where this really is a skill. They have figured something out.
31 pitchers have thrown enough innings to qualify for my study in each of the last three years (2019, 2021, 2022). Only 10 of them have posted xwOBACON's below .350 in each of the three years. Those names:
- Sandy Alcantara
- Chris Bassitt
- Luis Castillo
Only these 12 names have been able to keep the number under .375 in each season:
- Sandy Alcantara
- Chris Bassitt
- Luis Castillo
- Zack Wheeler
- Max Fried
- Lance Lynn
- Max Scherzer
- Marcus Stroman
- Tyler Mahle
- Joe Musgrove
- Adam Wainwright
- Zack Greinke
Variance has a strong hold on the numbers here. I would say that for Sandy, Fried, Bassitt, Castillo, Wheeler, Scherzer, and Musgrove - it's fine to expect strong performance in this category in 2023. For the rest of the league, I'm not going to bother with predictions here. We would probably be more accurate just predicting the league average.
Pitchers to Question
Knowing all of this, the logical conclusion here is to be wary of pitchers that posted very good xwOBACONs in 2022. Unless they're one of the names we just mentioned, it's a bit foolish to expect them to repeat that strong performance in 2023. Here are some of the names that stand out:
Tyler Anderson, Anaheim Angels
| 2022 K-BB% | 2022 xwOBACON | 2021 xwOBACON | 2019 xwOBACON | 2018 xwOBACON |
| 14.7% | .306 | .364 | -- | .349 |
Nobody is buying Anderson's 2.57 ERA from last year, but the Angels felt confident enough to give him a sizeable contract. Anderson's .306 xwOBACON was the lowest in the league, and it was a massive improvement on what he had done in the past. It's a near certainty that he adds 20+ points back to this total, which won't do him many favors with such a low K-BB%.
Cristian Javier, Houston Astros
| 2022 K-BB% | 2022 xwOBACON | 2021 xwOBACON | 2019 xwOBACON | 2018 xwOBACON |
| 24.3% | .308 | -- | -- | -- |
We haven't seen much of Javier in the Majors, so it is possible that he will eventually join the Alcantara ranks with the ability to stifle hard contact at an elite level year in and year out. For now, however, we should have our doubts. The good news is that there is plenty of room for regression here with the 24.3% K-BB%. If he maintains that, he'll be an ace - but some regression from the 2.54 ERA we saw last year is likely.
Dylan Cease, Chicago White Sox
| 2022 K-BB% | 2022 xwOBACON | 2021 xwOBACON | 2019 xwOBACON | 2018 xwOBACON |
| 20.3% | .310 | .380 | -- | -- |
Similar to Javier here. There's plenty to love like about the K-BB% above 20%. Cease was fantastic last year, and it's fine to consider him a very good pitcher for fantasy purposes. However, the .310 xwOBACON was an outlier outcome, and it's even more surprising when you see the .380 mark he put up in 2021. I think his performance in 2023 will fall firmly between these two numbers. That doesn't knock him out of the running to be an SP1 on your fantasy team, but it does make his newfound top-30 ADP seem a little bit unjustified.
Nestor Cortes, New York Yankees
| 2022 K-BB% | 2022 xwOBACON | 2021 xwOBACON | 2019 xwOBACON | 2018 xwOBACON |
| 20.3% | .316 | -- | -- | -- |
A third guy here with a great K-BB%, so less reason for concern. The 2022 season was the first time we saw Cortes get a large number of starts, and he did not disappoint. The K% was strong at 26%, but short of the heights of Javier and Cease. He does have that lefty deception thing going for him, but I won't be drafting Cortes aggressively and I think you could really see some movement in the wrong direction in his 2023 numbers.
Martin Perez, Texas Rangers
| 2022 K-BB% | 2022 xwOBACON | 2021 xwOBACON | 2019 xwOBACON | 2018 xwOBACON |
| 12.2% | .327 | .405 | .328 | -- |
Perez had gone on these runs of great starts without many strikeouts in the past, but the wheel fully fell off in 2021 as you can see there. He's not a strikeout pitcher, and he seems to have a run at least a little bit ahead of expectations in the contact-allowed categories last year. I don't expect anything close to another 2.89 ERA.
Tony Gonsolin, Los Angeles Dodgers
| 2022 K-BB% | 2022 xwOBACON | 2021 xwOBACON | 2019 xwOBACON | 2018 xwOBACON |
| 17.1% | .323 | .335 | .339 | -- |
Gonsolin had the second-best ERA in the league despite a K-BB% well below 20%. Hitters had all kinds of trouble squaring his pitches up, and that wasn't exactly anything new. He posted strong numbers here in both 2021 and 2019, so maybe he is one of these guys - but there's also the chance that it's just three fortunate seasons in a row and he'll have a bad year coming up. He's still not a guy the field is buying into with an ADP above 170, so I don't have any real criticism of picking him this year - but felt he deserved inclusion on this list.
Relievers with Really Low xwOBACONs
- Clay Holmes (.260)
- Tim Hill (.266)
- Wandy Peralta (.274)
- Brusdar Graterol (.275)
- Jason Adam (.276)
- Daniel Bard (.280)
- Devin Williams (.280)
- Jimmy Lambert (.284)
- Emmanuel Clase (.285)
Hope the list of names here helped, but my main point here is that if you see a pitcher that clearly benefited a ton from disallowing hard contact one year - hesitate to buy into them heavily in the next! We'll be back with more soon, happy 2023 everybody!
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