The advanced pitching metric SIERA was introduced in the golden age of sabermetric stat creation around 2010. Eric Seidman and Matt Swartz of Baseball Prospectus created Skill-Interactive Earned Run Average (SIERA) early in that year as a way to enhance some of the previously-developed ERA estimators such as Defense-Independent Pitching Statistics (DIPS), Fielding Independent Pitching (FIP), or QuickERA (QERA). We’re going to look at SIERA and use it to identify potential pitching sleepers for our upcoming drafts.
What is SIERA?
Their hope was that they could create a statistical model that would more accurately reflect outcomes that can and do affect a pitcher’s ERA. For example:
- Strikeouts are the best possible outcome in any situation for a pitcher
- Walks are an absolute killer to starting pitchers
- Groundballs are typically more advantageous to a pitcher than line drives or flyballs
- The park a pitcher calls home can account for huge swings in run prevention
SIERA takes all of these things into account, and – through an extremely complicated formula – spits out an estimated number that is very close to what we would see with an ERA total. If you want a deep dive into SIERA, you can check out a five-part tutorial over on Fangraphs.
2021 SIERA for Starting Pitchers
To find a few names for 2022 fantasy baseball drafts that might stand out based on SIERA, I first pulled the stat for all starting pitchers with at least 90 innings. There were 129 pitchers who fit those criteria. Here, just to quickly identify if SIERA aligns with ERA, are the top 50 starters by SIERA for 2021. Their ERA is also included.
| Pitcher | ERA | SIERA |
|---|---|---|
| Corbin Burnes | 2.43 | 2.61 |
| Max Scherzer | 2.46 | 2.90 |
| Gerrit Cole | 3.23 | 2.93 |
| Carlos Rodon | 2.37 | 2.96 |
| Clayton Kershaw | 3.55 | 3.10 |
| Logan Webb | 3.03 | 3.13 |
| Zack Wheeler | 2.78 | 3.18 |
| Robbie Ray | 2.84 | 3.21 |
| Aaron Nola | 4.63 | 3.26 |
| Brandon Woodruff | 2.56 | 3.31 |
| Freddy Peralta | 2.81 | 3.40 |
| Kevin Gausman | 2.81 | 3.42 |
| Trevor Bauer | 2.59 | 3.48 |
| Pablo Lopez | 3.07 | 3.49 |
| Yu Darvish | 4.22 | 3.49 |
| Ranger Suarez | 1.36 | 3.51 |
| Charlie Morton | 3.34 | 3.53 |
| Dylan Cease | 3.91 | 3.57 |
| Nathan Eovaldi | 3.75 | 3.60 |
| Alex Wood | 3.83 | 3.60 |
| Shohei Ohtani | 3.18 | 3.61 |
| Shane McClanahan | 3.43 | 3.62 |
| Julio Urias | 2.96 | 3.64 |
| Eduardo Rodriguez | 4.74 | 3.65 |
| Jose Berrios | 3.52 | 3.65 |
| Pitcher | ERA | SIERA |
|---|---|---|
| Sandy Alcantara | 3.19 | 3.68 |
| Sean Manaea | 3.91 | 3.68 |
| Joe Musgrove | 3.18 | 3.69 |
| Trevor Rogers | 2.64 | 3.72 |
| Lance Lynn | 2.69 | 3.72 |
| Lucas Giolito | 3.53 | 3.72 |
| Walker Buehler | 2.47 | 3.73 |
| Max Fried | 3.04 | 3.76 |
| Frankie Montas | 3.37 | 3.79 |
| Framber Valdez | 3.14 | 3.79 |
| Zach Eflin | 4.17 | 3.81 |
| Adbert Alzolay | 4.58 | 3.81 |
| Tyler Mahle | 3.75 | 3.82 |
| Andrew Heaney | 5.83 | 3.84 |
| Sonny Gray | 4.19 | 3.85 |
| Chris Bassitt | 3.15 | 3.86 |
| Logan Gilbert | 4.68 | 3.87 |
| Alek Manoah | 3.22 | 3.88 |
| Luis Garcia | 3.48 | 3.91 |
| Tarik Skubal | 4.34 | 3.92 |
| Cristian Javier | 3.55 | 3.93 |
| Marcus Stroman | 3.02 | 3.95 |
| Kenta Maeda | 4.66 | 3.98 |
| Michael Wacha | 5.05 | 4.00 |
| Lance McCullers Jr. | 3.16 | 4.02 |
As you can see, SIERA mostly does a good job of tracking which pitchers will also have a solid ERA. Those top ten especially look very close to a list of the top ten pitchers for the year. And seven of those top ten in 2021 SIERA are also going in the top ten in 2022 pitcher ADP, according to Fantrax’s latest data.
A few names initially stand out here. Both Yu Darvish and Ranger Suarez are back-to-back in the top 20. Their ERAs were both wildly different than their SIERAs in opposite directions. Darvish experienced some tremendous bad luck in the second half of 2021 so his ERA is about 0.8 higher than his SIERA. Suarez took the world by storm when he moved into the starting rotation, but his 1.36 ERA hid a good-not-great 3.51 SIERA.
Julio Urias, Trevor Rogers, and Walker Buehler were others who significantly outperformed their SIERA in 2021.
Finding SIERA Pitching Sleepers
But the more helpful exercise as we are neck-deep in 2022 fantasy baseball draft season is to see who had ERAs that significantly trailed their SIERA. Who, like Yu Darvish, was unlucky last season and might be due for some regression as we enter a new season? Many of the names on this list will end up being the biggest pitching sleepers of 2022.
Here are the top 50 starting pitchers with the largest gap between their final 2021 ERA and their SIERA.
| Pitcher | ERA | SIERA | Difference |
|---|---|---|---|
| Andrew Heaney | 5.83 | 3.84 | 1.99 |
| Jorge Lopez | 6.07 | 4.65 | 1.42 |
| Matt Harvey | 6.27 | 4.85 | 1.42 |
| Aaron Nola | 4.63 | 3.26 | 1.37 |
| JT Brubaker | 5.36 | 4.04 | 1.32 |
| Patrick Corbin | 5.82 | 4.61 | 1.21 |
| Mitch Keller | 6.17 | 4.98 | 1.19 |
| Erick Fedde | 5.47 | 4.30 | 1.17 |
| Chi Chi Gonzalez | 6.46 | 5.29 | 1.17 |
| Eduardo Rodriguez | 4.74 | 3.65 | 1.09 |
| Michael Wacha | 5.05 | 4.00 | 1.05 |
| Chris Paddack | 5.07 | 4.05 | 1.02 |
| Kolby Allard | 5.41 | 4.41 | 1.00 |
| J.A. Happ | 5.79 | 4.89 | 0.90 |
| Mike Minor | 5.05 | 4.20 | 0.85 |
| Logan Gilbert | 4.68 | 3.87 | 0.81 |
| Adbert Alzolay | 4.58 | 3.81 | 0.77 |
| Jose Urena | 5.81 | 5.06 | 0.75 |
| Yu Darvish | 4.22 | 3.49 | 0.73 |
| Kenta Maeda | 4.66 | 3.98 | 0.68 |
| Ryan Yarbrough | 5.11 | 4.45 | 0.66 |
| Wil Crowe | 5.48 | 4.86 | 0.62 |
| Brady Singer | 4.91 | 4.30 | 0.61 |
| Triston McKenzie | 4.95 | 4.36 | 0.59 |
| Josh Fleming | 5.09 | 4.51 | 0.58 |
| Pitcher | ERA | SIERA | Difference |
|---|---|---|---|
| Alec Mills | 5.07 | 4.50 | 0.57 |
| Brad Keller | 5.39 | 4.84 | 0.55 |
| Mike Foltynewicz | 5.44 | 4.90 | 0.54 |
| Ross Stripling | 4.80 | 4.35 | 0.45 |
| Jordan Lyles | 5.15 | 4.70 | 0.45 |
| Clayton Kershaw | 3.55 | 3.10 | 0.45 |
| Tarik Skubal | 4.34 | 3.92 | 0.42 |
| Jon Gray | 4.59 | 4.17 | 0.42 |
| Zach Davies | 5.78 | 5.36 | 0.42 |
| Dane Dunning | 4.51 | 4.12 | 0.39 |
| Nick Pivetta | 4.53 | 4.15 | 0.38 |
| Zach Eflin | 4.17 | 3.81 | 0.36 |
| Dylan Cease | 3.91 | 3.57 | 0.34 |
| Sonny Gray | 4.19 | 3.85 | 0.34 |
| German Marquez | 4.40 | 4.07 | 0.33 |
| Gerrit Cole | 3.23 | 2.93 | 0.30 |
| Dallas Keuchel | 5.28 | 5.01 | 0.27 |
| Zac Gallen | 4.30 | 4.04 | 0.26 |
| Yusei Kikuchi | 4.41 | 4.16 | 0.25 |
| Austin Gomber | 4.53 | 4.29 | 0.24 |
| Alex Wood | 3.83 | 3.60 | 0.23 |
| Sean Manaea | 3.91 | 3.68 | 0.23 |
| Martin Perez | 4.74 | 4.52 | 0.22 |
| Hyun-Jin Ryu | 4.37 | 4.17 | 0.20 |
| Caleb Smith | 4.83 | 4.68 | 0.15 |
This list can help us identify some potential 2022 sleepers, especially if we consider them in their current context. Some pitchers, such as Matt Harvey, had both terrible ERAs and SIERAs, so we can ignore those gaps. Some pitchers, such as Aaron Nola, are already uncovered secrets and have a high cost right now. But others gain a tremendous amount of respectability when you dig into the numbers and are still very affordable at the draft table.
Andrew Heaney
Heaney has almost two full runs of difference between his 2021 ERA (5.83) and his 2021 SIERA (3.84). That is a monstrous difference and this was by far Heaney’s highest ERA since he pitched just 21 innings in 2017.
Last year, Heaney was snake-bitten by the combination of a 44% fly ball rate plus an 18.1% HR/FB ratio, which were both his highest since that short sample in 2017. In addition to the home runs, he also carried his worst LOB% of his career at just 67.4%. League average in 2021 was over 72%, so some gains in that department would go a long way to keeping the ERA down.
Heaney seems to have the inside track on the fifth starter’s spot for his new team, the Los Angeles Dodgers. The checkered injury history of Clayton Kershaw should help to keep him in that rotation all season, and now he calls Dodger Stadium home. His new park ranks 14th in overall offensive park factor the last three seasons while Angel Stadium ranks eighth.
Heaney is basically free in standard drafts with an ADP of 305.6. At that price, you can certainly pay off the investment with just minor improvements to his surface stats.
Eduardo Rodriguez
While Eduardo Rodriguez had a HR/FB ratio that was in line with his career norms, he also had a career-low LOB%. His 68.9% in that department was 9% lower than in 2019 (his last season to pitch) and more than five percent below his career average.
E-Rod had the highest K/9 of his career and the lowest BB/9, so everything else trended in the right direction for the 28-year-old pitcher. All of his pitch velocity was within a minor degree of the rest of his career and his swinging strike rate mirrored what it had been the last three seasons.
This just looks like the classic case of the balls bouncing in the wrong spot when men were on base and should be something that course-corrects in 2o22. Rodriguez’s ADP is currently 139.8 but I would have no issue taking him 15-20 picks higher.
Triston McKenzie
The 24-year-old fireballer only has a 153-inning track record in parts of two years in the majors. But if the gains he made in the second half of 2021 can stick around, this is the definition of a diamond in the rough at an ADP of 211.3 this year and he has the highest upside of any of these potential pitching sleepers.
What stands out most in McKenzie’s profile is his ability to miss bats. Last year, among all pitchers with at least 100 innings pitched, McKenzie ranked 25th in swinging strike percentage (12.6%) and combined that with a called strike rate of almost 15%. He had a 10.2% K/9 rate which contributed to his elite 27.5% strikeout rate.
But the biggest gains he made in 2021 were in the walk rate as the season progressed. In the first half last season, McKenzie’s walk rate was an abysmal 7.3 BB/9. That paved the way to a 1.7 K/BB walk rate which is not even replacement level in the majors. But in the second half, his BB/9 rate went down to 2.29, which caused the K/BB rate to spike to 3.78. McKenzie never had a walk rate higher than 2.92 in his first five years in the minors, so assuming he has that fixed, this is a pitcher who could also easily outgain his draft price.