RADIO
Skills-Interactive ERA (or SIERA) has been around since 2011 when it was introduced at Baseball Prospectus by Matt Swartz and Eric Seidman before moving to its current home at Fangraphs. Much like xFIP, SIERA attempts to quantify the skills that underpin a pitcher's ERA, albeit in a different manner. Although technically a backward-looking evaluator, SIERA is slightly more predictive than xFIP in terms of the following year's ERA and most gets at the how and why of a pitcher's success.
FIP and xFIP generally ignore balls in play, focusing on only the things that pitchers can directly control; strikeouts, walks/HBP, and home runs. SIERA tries to take into account how specific skills (strikeouts, walks, ground balls) interact with each other in order to help pitchers limit runs. Strikeouts are even more valuable in SIERA, as high-K pitchers induce more weak contact, thereby running lower BABIPs and HR/FB%. Walks are bad but not as bad if you don't allow many of them, as they have a lesser chance to hurt you. The more groundballs you allow, the easier they are to field and the more double-play opportunities you'll have.
Essentially, instead of giving "flat-rates" for different skills, SIERA weights them, moving up the skills of pitchers who have high strikeout- or groundball-rates, or low walk-rates. While SIERA is not the "final word" in ERA evaluators (as different evaluators have strengths in different areas), it is quite sticky in terms of the following year's ERA. Let's start today by looking at three pitchers being taken around the top-100 who had large gaps between their 2019 ERA and SIERA and see what can be expected in 2020.
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Largest ERA Overachievers in 2019
Looking at starters in the top-300 of ADP in NFBC leagues, we'll start with the 25 biggest differences between their ERA and SIERA last season. For sake of consistency, I'll be using dollar values derived via the Fangraphs auction calculator for 5x5 standard 12-team leagues.
| Player | ADP | ERA | SIERA | DIFF | K% | BB% | GB% |
| Jacob deGrom | 7 | 2.43 | 3.29 | -0.86 | 31.7% | 5.5% | 44.4% |
| Jack Flaherty | 22 | 2.75 | 3.68 | -0.93 | 29.9% | 7.1% | 39.5% |
| Mike Clevinger | 29 | 2.71 | 3.31 | -0.60 | 33.9% | 7.4% | 40.8% |
| Clayton Kershaw | 41 | 3.05 | 3.77 | -0.72 | 26.8% | 5.8% | 48.0% |
| Luis Castillo | 42 | 3.40 | 3.95 | -0.55 | 28.9% | 10.1% | 55.2% |
| Patrick Corbin | 46 | 3.25 | 3.88 | -0.63 | 28.5% | 8.4% | 49.5% |
| Chris Paddack | 53 | 3.33 | 3.83 | -0.50 | 26.9% | 5.5% | 40.2% |
| Zack Greinke | 63 | 2.93 | 3.96 | -1.03 | 23.1% | 3.7% | 45.2% |
| Tyler Glasnow | 65 | 1.78 | 3.18 | -1.40 | 33.0% | 6.1% | 50.4% |
| Jose Berrios | 78 | 3.68 | 4.28 | -0.60 | 23.2% | 6.1% | 42.1% |
| Sonny Gray | 99 | 2.87 | 3.97 | -1.10 | 29.0% | 9.6% | 50.8% |
| Frankie Montas | 101 | 2.63 | 3.76 | -1.13 | 26.1% | 5.8% | 49.4% |
| Mike Soroka | 106 | 2.68 | 4.28 | -1.60 | 20.3% | 5.9% | 51.2% |
| Zac Gallen | 124 | 2.81 | 4.24 | -1.43 | 28.7% | 10.8% | 38.9% |
| Eduardo Rodriguez | 133 | 3.81 | 4.31 | -0.50 | 24.8% | 8.7% | 48.5% |
| Hyun-Jin Ryu | 144 | 2.32 | 3.77 | -1.45 | 22.5% | 3.3% | 50.4% |
| Kyle Hendricks | 156 | 3.46 | 4.38 | -0.92 | 20.6% | 4.4% | 41.3% |
| Mike Minor | 173 | 3.59 | 4.51 | -0.92 | 23.2% | 7.9% | 40.0% |
| Jake Odorizzi | 181 | 3.51 | 4.14 | -0.63 | 27.1% | 8.1% | 35.0% |
| Luke Weaver | 197 | 2.94 | 3.84 | -0.90 | 26.5% | 5.4% | 40.7% |
| Marcus Stroman | 204 | 3.22 | 4.41 | -1.19 | 20.5% | 7.5% | 53.7% |
| Aaron Civale | 250 | 2.34 | 4.74 | -2.40 | 20.3% | 7.1% | 40.5% |
| Sandy Alcantara | 262 | 3.88 | 5.28 | -1.40 | 18.0% | 9.7% | 44.6% |
| Dallas Keuchel | 272 | 3.75 | 4.39 | -0.64 | 18.7% | 8.0% | 60.1% |
| Yonny Chirinos | 279 | 3.54 | 4.25 | -0.71 | 21.5% | 5.3% | 43.3% |
Zack Greinke, Houston Astros
2019: 2.93 ERA, 3.96 SIERA (1.03 runs differential)
Greinke had another resurgence in 2019, finishing as SP 4 (#24 overall) according to the Fangraphs auction calculator with $26 in fantasy earnings. Even though his fastball has been topping out at around 90 mph for the past three years, Greinke commands the strike zone with supreme control, steadily mixing and matching a mostly four-pitch mix:
| Pitch | 2019 | 2018 | 2017 |
| Four-Seam | 41% | 43% | 39% |
| Changeup | 22% | 21% | 16% |
| Slider | 16% | 17% | 22% |
| Curveball | 15% | 11% | 13% |
| Two-Seam | 5% | 5% | 9% |
Although, I would also be remiss if I fail to acknowledge his ownership of one of baseball's most entertaining pitches. Presenting, the Eephus:
Greinke ended as a top-five pitcher on the strength of 18 wins, a 2.93 ERA, and a 0.96 WHIP - which were all the highest marks he's posted since 2015:
| Season | G | IP | W | SO | K% | BB% | WHIP | ERA |
| 2015 | 32 | 222.2 | 19 | 200 | 23.7% | 4.7% | 0.84 | 1.66 |
| 2016 | 26 | 158.2 | 13 | 134 | 20.1% | 6.2% | 1.27 | 4.37 |
| 2017 | 32 | 202.1 | 17 | 215 | 26.8% | 5.6% | 1.07 | 3.20 |
| 2018 | 33 | 207.2 | 15 | 199 | 23.7% | 5.1% | 1.08 | 3.21 |
| 2019 | 33 | 208.2 | 18 | 187 | 23.1% | 3.7% | 0.98 | 2.93 |
Putting aside a bonkers season in 2015, Greinke has been mostly a consistent performer these past years. He's not going to strike out a ton of batters but he won't walk many either. And being the true definition of an innings-eater - having pitched over 200 IP in nine of his last 12 seasons - Greinke goes deep enough in games to pile up wins, finishing with at least 15 W in 10 of those 12 years.
Greinke turned back the clock with his ratios but how true is the 2.93 ERA? And how true has it stayed over these last few years?
| Season | ERA | FIP | xFIP | SIERA |
| 2015 | 1.66 | 2.76 | 3.22 | 3.27 |
| 2016 | 4.37 | 4.12 | 3.98 | 4.11 |
| 2017 | 3.20 | 3.31 | 3.34 | 3.48 |
| 2018 | 3.21 | 3.71 | 3.44 | 3.60 |
| 2019 | 2.93 | 3.22 | 3.74 | 3.96 |
Prior to 2019, Greinke's ERA had mostly stayed in line with it's evaluating metrics, outside of the aforementioned 2015. However, the evaluators say otherwise about his sub-three ERA last season. A 3.22 FIP doesn't speak too poorly of the intrinsic baseball value of his 2.93 ERA but a 3.74 xFIP and 3.96 SIERA don't speak as grandly about the skills that underpinned it.
Looking at the metrics that drive SIERA, it's easy to see why it wasn't a fan. Greinke's 23.1% K-rate was 49th among starters with at least 100 IP and his 45.2% groundball-rate was 42nd. Where Greinke shined was with a minuscule (and career-low) 3.7% walk-rate that was the third-best in baseball.
2020 Outlook (63 ADP on NFBC)
Taking a look at the various 2020 projection systems, it doesn't seem like SIERA and I are the only ones doubting that Greinke will be able to repeat his earned-runs feat (and value) from 2019:
| G | IP | W | SO | WHIP | ERA | FIP | $ Value | Rank (All) | Rank (SP) | |
| BAT | 32 | 199 | 15 | 187 | 1.15 | 3.86 | 4.22 | $16.8 | 63rd | SP 15 |
| ATC | 31 | 194 | 15 | 182 | 1.16 | 3.78 | 3.94 | $16.0 | 78th | SP 17 |
| DEPTH | 32 | 199 | 14 | 185 | 1.18 | 4.09 | 4.24 | $11.0 | 121st | SP 24 |
| Steamer | 32 | 202 | 14 | 183 | 1.24 | 4.26 | 4.31 | $5.9 | 171st | SP 34 |
| ZiPS | 30 | 179.7 | 13 | 172 | 1.12 | 3.91 | 4.18 | $13.0 | 91st | SP 21 |
Barring an unexpected transformation, Greinke won't see a significant jump in strikeouts and will need to rely on the other categories to carry him to fantasy success. Given his appetite for innings and having one of baseball's best offenses supporting him, wins shouldn't be an issue. If you could guarantee me 20 wins, I might be talked into something near his current ADP. But then again, probably not.
Being more apt to place him closer to a 4.oo ERA than another 3.00 ERA, I'm certainly the low-man among the RotoBaller rankers, putting Greinke at #119 overall in our latest update. I won't deny that it's an aggressive move but it's not just the lack of strikeouts and a substandard ERA that have me playing the role of Doubting Nicklaus.
It's also the fact that he's now 36-years-old, sits 89 mph with his fastball, and just gave up his lowest HR/9 (and HR/FB%) since 2015, even in the midst of baseball's historic offensive year. When the end comes for Greinke, it may come quickly. And I don't want to be the one holding the bag on someone with such limited upside.
Do you know what you get with around a 4.00 ERA, 185 strikeouts, and 14 wins?
Eduardo Rodriguez (134 ADP in NFBC).
Sonny Gray, Cincinnati Reds
2019: 2.87 ERA, 3.97 SIERA (1.10 runs differential)
After a disastrous 2018 spent in pinstripes, it was a resurgent year from Gray in his first year with the Reds, posting his lowest ERA since 2015 and finishing as SP 14 in 12-team leagues and #69 overall. That may have been nice but the one-run difference in his SIERA begs the question of whether we should pump the brakes on the Queen City southpaw. Will we get 2018 or 2019's version of Gray in 2020?
| Season | Team | G | IP | W | SO | K% | BB% | WHIP | GB% | Hard% | ERA | FIP | xFIP | SIERA |
| 2018 | Yankees | 30 | 130.1 | 11 | 123 | 21.1% | 9.8% | 1.50 | 50.0% | 35.5% | 4.90 | 4.17 | 4.10 | 4.28 |
| 2019 | Reds | 31 | 175.1 | 11 | 205 | 28.9% | 9.6% | 1.08 | 50.8% | 38.1% | 2.87 | 3.42 | 3.65 | 3.97 |
None of the ERA evaluators liked Gray's ERA that much but SIERA was the laggard at 3.97. However, unlike Greinke before him, Gray has some favored tools in the SIERA-toolbox that could lead to a lower number in 2020.
His 9.6% walk-rate was not one of those tools, finishing 100th out of 113 starters with at least 100 innings and was actually better than his 10.8% xBB%. But Gray does have a tool in that he's a ground-ball machine, with his 50.8% GB% finishing as the 12th-highest. And that mark is low, relative to his 52.9% career average. Armed with two pitches (four-seam, curveball) that have rates over 60%, Gray has the track-record to elevate his groundball-rate even higher.
Much of his final line looks like other years but it's the strikeout-rate that jumps off of the page. Having never had above a 22.6% K-rate in a full season, Gray popped off for a 28.9% K-rate in 2019 after a 21.1% K-rate in 2018. In terms of whiffery, he essentially transformed from Tanner Roark to Walker Buehler.
The best predictor of a future K-rate is the past K-rate and 30-year-olds generally don't suddenly jump nine-points due to happenstance. So, what happened?
Pitch Mixed Up
2018 was certainly a low-point for his career but Gray has been candid about his clashes with the Yankees and their development team. In an interview($) with Eno Sarris last spring, the new Reds hurler broke down those issues, including New York's insistence that he throw his slider in the zone more, hoping they could duplicate the success that they had with Masahiro Tanaka.
The problem - in Gray's own words - is that he can't control his slider. His is of the big and sweeping variety that he wants to induce chases with. Instead, he was being told to try and force it in the zone. Take a look at the heat maps between 2018 and 2019 and see this difference in action:
In addition to being uncomfortable throwing a pitch he couldn't command (and to spots he didn't want to), throwing the slider as such led to Gray's biggest weapon, the curveball, losing its shape and effectiveness.
This had been a problem for him even back in his days at Vanderbilt, with his old college coach going so far as to ban the slider in order to make sure the curve stayed sharp. Once again, the heatmaps tell the story:
Spin Doctor
Besides getting his curveball and slider back on point, Gray also went back to the lab in order to better understand how to be most effective with his four-seamer. At 2527 rpm, Gray's fastball had the sixth-highest spin among starter who threw at least 500 of them in 2019. However, his spin-efficiency (the amount of spin that translates to movement) is incredibly low, sitting in the 40-45% range due to his arm slot not being conducive to getting a rise out of his heater.
By adjusting his arm-slot, Gray was able to increase the spin-efficiency and rise of his four-seamer but not consistently and not in a manner that felt natural on his arm. So instead of trying to force a square peg in a round hole, Gray leaned into the natural cutting action his four-seamer has, instead of trying to increase the rise.
The results were significant in many areas, as batters were unable to square the ball as well as they had in 2018. The average exit velocity dropped from 92.5 mph to 90.4 mph and the barrel-rate moved from an 11.9% Brl% to a 10.2% Brl% in 2019.
Knowing what we now know about the differences in Gray's arsenal in 2018 versus 2019, more context is added to the jump in strikeout-rate, as well as the 4.90 ERA he ran with the Yankees two years ago.
2020 Outlook ( 98 ADP in NFBC)
With an increased strikeout-rate and an already elite groundball-rate, Gray seems custom-made to outperform his SIERA in 2020. But the new K-rate will need to stick unless he's able to shave a few points off his substandard walk-rate. The issue is that everything needs to go just right for the lefthander in 2020 if you're counting on him returning his top-100 draft price. Because even with a near-30% K-rate and sub-3.00 ERA, Gray still finished #69 in earnings in 2019.
Looking at 2020 projections there doesn't seem to be much belief in a repeat performance:
| IP | W | SO | WHIP | ERA | $ Value | |
| THE BAT | 175 | 11 | 183 | 1.29 | 3.88 | 166th |
| ATC | 175 | 12 | 188 | 1.26 | 3.72 | 138th |
| Depth Charts | 175 | 12 | 190 | 1.26 | 3.87 | 135th |
| Steamer | 175 | 11 | 191 | 1.31 | 3.93 | 164th |
| ZiPS | 158 | 11 | 171 | 1.21 | 3.82 | 141st |
Even if the best-case scenario of a 2019 repeat comes to pass, Gray would likely only out-earn his draft-price by a few rounds. If he falls to the 120-130 range, then the upside makes him worth the price but I'm staying away at his current level.
Mike Soroka, Atlanta Braves
2019: 2.68 ERA, 4.28 SIERA (1.60 runs-differential)
This wouldn't be a proper overachievers article without the Braves rookie making an appearance. How big was Soroka's 1.60 run-differential between his 2.68 ERA and 4.28 SIERA? Looking at the top-60 starters according to the Fangraphs auction calculator, only three sported a larger difference; Aaron Civale (2.40), Dakota Hudson (1.72), and Zach Davies (1.88).
Soroka does quite well in two of the areas that SIERA prizes, with a 50.2% GB% that was the 10th-highest among starters and a 5.9% walk-rate that was the 24th-lowest. It's the strikeout-rate that lags behind and not by a small amount; of the top-50 starters, only Jeff Samardzija (18.9%), John Means (19.0%), and Mike Fiers (16.7%) had lower than Soroka's 20.3% K-rate.
He utilizes a four-pitch mix but his main weapon is the two-seam fastball that he threw more times than anyone besides Zach Davies. Utilized 45% of the time in 2019, Soroko's sinker doesn't get many swings-and-misses (5.6% SwStr%) but is a prime worm-burner, posting a 63.7% GB% that was the fifth-highest in baseball. However, the longer the season went, the more batters started to hone in:
*Graph courtesy of Alex Chamberlain's Pitch Leaderboard
And yet, even with few strikeouts, and his main pitch getting hit more and more, Soroka still finished as SP 16, just behind Lucas Giolito and just in front of Luis Castillo, Patrick Corbin, and Chris Paddack. Digging into his fantasy earnings by category, it's easy to see what carried the water:
| mW | mERA | mWHIP | mSO |
| $3.80 | $4.20 | -$1.00 | $1.20 |
Soroka is backed by what is expected to an above-average offense and his 6.0 IP/start was the 24th-highest among starters. So it's reasonable to think that his 13 wins from 2019 could be on the table again. But how likely is he to put up that sparkling ERA again, given that a graph of his evaluators looks like Cliff Hanger on Price is Right? Feel free to yodel along at home:
2020 Outlook (106 ADP in NFBC)
It can't be said enough; earning top fantasy value without a top strikeout-rate is possible but very challenging due to the all of the value-pressure put on the other categories. Any creep in your ratios or drop in your wins can quickly make your overall value plummet.
Taking a look at what the projections see, it seems only Dan Szymborski and his magical ZIPS machine believes that Soroka will give you a good return-on-investment in 2020.
| IP | W | SO | WHIP | ERA | $ Value | |
| THE BAT | 182 | 12 | 150 | 1.24 | 3.81 | 137th |
| ATC | 175 | 12 | 150 | 1.23 | 3.58 | 124th |
| Depth Charts | 182 | 11 | 159 | 1.23 | 3.72 | 131th |
| Steamer | 189 | 12 | 166 | 1.29 | 4.09 | 212th |
| ZiPS | 176 | 11 | 154 | 1.16 | 3.32 | 68th |
Soroka finished 81st-overall in value last year and is currently being drafted around a 108 ADP. Unless you're banking on a big strikeout jump that no one else sees, to pay off that draft-price Soroka will have a very small margin on any rise to his ERA. Personally, I think that ATC's projected line seems like a reasonable best-case scenario but I'd still take the over on his ERA. This means a hard pass for me and our latest staff ranking reflect that feeling, as I have ranked far below his ADP, at 145 overall.
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