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Welcome back to RotoBaller’s Statcast pitcher Studs and Duds article series! Each week I will select an advanced stat, choose two top performers and two under-performers, and analyze what those stats could mean for future fantasy output. In week 6 I wrote an article about SIERA Studs and Duds and alluded to a future article where I would compare pitchers' ERA to their SIERA. Well, that time has arrived!
SIERA quantifies a pitcher's performance by trying to eliminate factors the pitcher can't control on their own while also considering batted-ball profile. The formula can be found here for those who want to get into the nitty gritty. SIERA is a better indicator of a pitcher's performance than ERA and can help predict future success or failure compared to a pitcher’s current ERA. As such, finding pitchers with large ERA-SIERA discrepancies is a great way to help identify potential buy-low and sell-high candidates.
This week I will look at two pitchers whose ERA has been higher than their SIERA (indicating some potential positive regression in the future) and two whose ERA has been lower than their SIERA (indicating some potential negative regression in the future). As I have mentioned in previous articles, I will not focus on obvious fantasy studs, but will choose to analyze more under-the-radar/less-obvious players or studs who have been struggling to give readers the most useful insight. Before we dive in I would like to say a quick thank you to all of the RotoBaller followers who stop by to read these articles. This will be my 100th career article with RotoBaller and I am looking forward to providing you with many more covering fantasy baseball insights!
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ERA-SIERA Studs
All stats current as of Sunday, June 21.
Luis Castillo, Cincinnati Reds
(2-10, 5.61 ERA, 4.36 SIERA)
Our first pitcher has been a higher-end fantasy option throughout his career, but has been one of fantasy's biggest disappointments so far this season. Luis Castillo had a career 3.62 ERA and 27% strikeout rate coming into this season but has a poor 5.61 ERA and 20.9% strikeout rate through 15 starts this season. Many frustrated fantasy managers have likely been wondering what to do with him, but I may be able to provide some good news given his 4.36 SIERA. What could his ERA-SIERA discrepancy mean for his performance for the rest of the season?
We'll focus on one of the key aspects of SIERA first: batted-ball profile. Castillo actually has a solid batted-ball profile this season. Both his average exit velocity and hard-hit rate are in the top- 35% of baseball, and he has kept the ball on the ground with a 6.4-degree launch angle. However, he has a .327 BABIP this season, suggesting that he has gotten unlucky. Castillo hasn't located his fastballs overall, which may be contributing to his low strikeout rate. However, he has kept his changeup down in the zone, so I would expect some positive regression there as well simply due to his career mark.
As additional evidence, Castillo has pitched better overall lately. He has posted a solid 2.19 ERA and 14% swinging-strike rate over his last four starts, so he is definitely taking steps in the right direction. Given his career numbers and his recent performance, there is no reason to think that Castillo won't experience some more positive regression as the season continues.
Castillo's surface numbers have been ugly this season, and he has been a fantasy nightmare through the first few months. However, his solid batted-ball profile and SIERA, coupled with his other unusually high underlying metrics indicate that he has gotten unlucky and should be performing better, which he has done lately. Hopefully, Castillo will continue his relative upward trajectory to finish out the first half of the season. If he does, now may be the final opportunity to attempt to buy low on him on what could be a huge fantasy steal.
Brady Singer, Kansas City Royals
(3-5, 4.76 ERA, 4.05 SIERA)
Our second pitcher is one who was hyped in fantasy dynasty leagues but got the call early in 2020 due to the shortened season. Brady Singer is just one of a bunch of Royals' pitching prospects, but he hasn't really pitched like one this season, compiling a 3-5 record with a 4.76 ERA and 1.43 WHIP. However, his SIERA indicates that there may be some hope for him this season. Let's take a closer look.
There are some good signs upon looking under the hood. Singer has also maintained a strong batted-ball profile this season. His average exit velocity and hard-hit rate are both in the top-25% of baseball, and his 7.1-degree launch angle is respectable. Singer's .340 BABIP is also a good deal higher than his .303 career mark, although he does not have the same track record to go off of compared to Castillo.
While Singer's SIERA indicates he has gotten unlucky in terms of his ERA, I feel his strikeout value will remain limited. He has essentially relied on two pitches as a starter this season, which I don't feel is sustainable. His slider is an effective swing-and-miss pitch with a 17.9% swinging-strike rate, but his sinker has gotten too much of the plate to be a solid complementary pitch. Singer will likely need to develop a third pitch in order to become an above-average strikeout starter.
The good sign for Singer is that it does look like he has gotten unlucky this season given his SIERA and batted-ball profile. However, he does not have many big-league numbers to go off of, so it is harder to say how things could pan out for him for the rest of the season. I think his two-pitch mix limits his strikeout potential and therefore his overall fantasy value. He certainly holds plenty of fantasy value in dynasty leagues and will likely be a useful streamer, but I would like to see some more solid production from him before buying into him.
Singer was removed from his last start for precautionary reasons (shoulder), but is scheduled to start against the Yankees on Tuesday so there doesn't appear to be any need for alarm.
ERA-SIERA Duds
All stats current as of Sunday, June 20.
Lance Lynn, Chicago White Sox
(7-3, 2.02 ERA, 3.62 SIERA)
I would be remiss if I didn't write about Lance Lynn at some point in the season with regards to SIERA. The veteran has had a knack for out-performing his SIERA over the course of his career, but this season has been an outlier even in that. Lynn has been outstanding this season, compiling a minuscule ERA just over two with an excellent 28.1% strikeout rate. However, his 3.62 SIERA, while still good overall, is much higher than his ERA. With a career season underway, could Lynn's ERA-SIERA discrepancy spell trouble for him in the future?
The analysis here is essentially same old Lance Lynn. He has relied heavily on his mix of four-seam fastball, cutter, and sinker, which have a lot of spin on them but aren't overpowering in terms of velocity. This has always been Lynn's approach and he has managed to find strikeout success with his fastball arsenal, as indicated by both his strikeout rate and the fact that he has near double-digit swinging strike rate percentages with all three pitches.
He has also used those three pitches in a similar manner to previous seasons, moving them around the zone but not achieving the best locations. His batted-ball profile confirms this, as his average exit velocity and hard-hit rate are both just below league average, and his 19.7-degree launch angle is less than ideal.
Lynn presents an interesting case here. On the one hand, he has been one of baseball's best pitchers this season. Lynn typically outperforms his SIERA and his current SIERA is still solid. On the other hand, the large gap between his ERA and SIERA and his unusually low ERA suggests that there should be some negative regression coming. Fantasy managers who have rostered Lynn to this point may be hard-pressed to sell-high on Lynn knowing that he will still be a valuable fantasy pitcher even if he experiences regression. Given all the evidence, I think it makes sense to stick with Lynn unless fantasy managers can get a huge haul in return.
Kyle Gibson, Texas Rangers
(4-0, 2.09 ERA, 4.26 SIERA)
Our final pitcher seems to be a useful fantasy streamer at some point each season, but typically finishes with lackluster overall numbers. This season has been different for Kyle Gibson, who has a strong 2.09 ERA and 1.03 WHIP through 13 starts. His surface numbers look good, but his 4.23 SIERA suggests that the same mediocre pitcher may be lurking underneath. What can fantasy managers expect from Gibson as the season progresses?
The interesting thing here is that a lot of Gibson's numbers under the hood look similar to those of previous seasons. His batted-ball profile is decent with slightly above-average exit velocity and hard-hit metrics and an 8.2-degree launch angle. He has also done a similar job of locating his pitches out of the middle of the zone for the most part.
Despite pitching seemingly as he always has, some of Gibson's metrics are much improved. For instance, his expected stats are all in about the top-30 percent of baseball, and his barrel rate is uncharacteristically in the 91st percentile of baseball. Consequently his BABIP, which has a career mark of .305, is at a career-low .244. This presents a curious case in which we can identify some of the reasons why Gibson has succeeded this season, but he has pitched the same as he has in the past and his SIERA indicates as much.
Gibson's story is a bit difficult to parse out. That being said, I would tend to side with both his SIERA and his career track record. It doesn't appear that he has made any fundamental changes to his game, so I would say his sudden success is an outlier that could regress back towards his career averages. As such, I would consider him to be a sell-high candidate. He may not garner a ton of interest, but there are always fantasy managers out there trying to snatch up hot pitchers.
A special mention to Taiwan Walker, who I wrote about in week 6's SIERA article. He is another Lance Lynn-like pitcher who always seems to outperform his SIERA.
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