MLB: Jeff Zimmerman on Starter/Reliever Splits

MLB: Jeff Zimmerman on Starter/Reliever Splits

I cringe every time Carlos Hernandez is brought up in conversation. He was a serviceable pitcher with a 3.68 ERA, 1.28 WHIP and 7.8 K/9. The deal is that there were two separate sides to this profile. 

In the 13 games in which he pitched in relief, he posted a 11.9 K/9 while that number dropped to 5.9 K/9 in his 11 starts. His fastball velocity started out at 98 mph. While he was able to maintain it for a bit, it dropped to 96.6 mph over his last four starts. Also, he couldn't maintain his production the second time through the order with a 2.96 FIP the first time through and a 5.75 FIP the second time. Simply, he had a 5 K-BB% as a starter. Dallas Keuchel was the only qualified pitcher to have anything close to a 5 K-BB% (next closest was Cole Irvin at 11%). If the innings threshold is dropped to 100 IP, some comparables are John Gant, Jose Urena, Jon Lester, Zach Davies.

My goal is not to beat up on Carlos Hernandez, but he's an example of a 2021 pitcher who had two different starter and reliever profiles. Today, I'm going to dig into several more of these arms who transitioned from starter to reliever.

In all, there were 65 pitchers who started five games and relieved in five games in 2021.

 As Starter    As Reliever    
NameGIP

I cringe every time Carlos Hernandez is brought up in conversation. He was a serviceable pitcher with a 3.68 ERA, 1.28 WHIP and 7.8 K/9. The deal is that there were two separate sides to this profile. 

In the 13 games in which he pitched in relief, he posted a 11.9 K/9 while that number dropped to 5.9 K/9 in his 11 starts. His fastball velocity started out at 98 mph. While he was able to maintain it for a bit, it dropped to 96.6 mph over his last four starts. Also, he couldn't maintain his production the second time through the order with a 2.96 FIP the first time through and a 5.75 FIP the second time. Simply, he had a 5 K-BB% as a starter. Dallas Keuchel was the only qualified pitcher to have anything close to a 5 K-BB% (next closest was Cole Irvin at 11%). If the innings threshold is dropped to 100 IP, some comparables are John Gant, Jose Urena, Jon Lester, Zach Davies.

My goal is not to beat up on Carlos Hernandez, but he's an example of a 2021 pitcher who had two different starter and reliever profiles. Today, I'm going to dig into several more of these arms who transitioned from starter to reliever.

In all, there were 65 pitchers who started five games and relieved in five games in 2021.

 As Starter    As Reliever    
NameGIPK/9WHIPERAGIPK/9WHIPERA
Adbert Alzolay21106.19.11.25.16819.19.80.931.4
Adrian Sampson5246.81.083511.17.91.062.38
Alec Mills2099.16.51.384.81219.26.91.736.41
Andrew Heaney2312010.51.275.4879.29.31.9710.24
Anthony Kay520.111.11.484.43613.19.51.957.43
Cal Quantrill221217.41.153.121828.26.91.291.88
Caleb Smith135710.31.66.953256.29.41.152.7
Carlos Hernandez1158.15.91.253.551327.111.91.353.95
Chad Kuhl14677.81.364.431413.111.51.86.75
Chase Anderson936.16.71.546.94511.26.21.296.17
Chi Chi Gonzalez188751.526.62614.24.91.575.52
Collin McHugh71290.580305210.71.021.9
Cristian Javier948.210.71.033.142752.212.31.333.93
David Price1141.17.41.163.922832.16.71.764.18
Dinelson Lamet929.19.51.433.991317.213.21.585.09
Drew Rasmussen104260.761.93253411.91.473.97
Drew Smyly23115.28.51.384.756116.51.271.64
Garrett Richards22110.17.11.655.221826.19.61.373.42
Humberto Castellanos73451.445.56711.27.71.23.09
Jake Woodford8375.81.414.141830.27.61.273.82
Jakob Junis627.110.21.244.6110127.51.756.75
J.C. Mejia1142.17.71.89.786109.90.81.8
Jeff Hoffman11457.81.675.2202812.91.433.54
Jesus Luzardo1885.19.31.616.2271091.79.9
John Gant2189.27.31.574.421820.18.41.232.66
Jorge Lopez25113.18.11.686.3588.110.80.962.16
Jose Quintana103513.12.068.23192810.91.324.18
Jose Suarez14717.51.284.44927.18.61.11.98
Jose Urena18835.91.635.96817.26.61.475.09
Josh Fleming1156.16.21.516.2315484.91.173.75
Justin Steele943.27.81.444.951113.114.21.052.03
Justus Sheffield1573.27.21.786.4866.25.42.5510.8
Keegan Akin17777.61.656.97188.51.285.5
Keegan Thompson616.17.71.95.512637101.32.43
Kolby Allard1791.26.61.215.4153310.11.455.45
Kris Bubic20103.281.414.77926.17.51.293.08
Kwang Hyun Kim2196.26.91.273.636105.41.41.8
Martin Perez221007.71.524.7714147.71.434.5
Matt Moore1356.18.11.76.551116.26.51.25.4
Matt Peacock8346.41.685.292752.14.51.494.64
Matt Shoemaker1150.261.587.2859.25.62.0712.1
Michael King624.27.31.585.471638.29.81.092.33
Michael Wacha23107.18.61.264.53617.19.91.628.31
Nestor Cortes1473.19.21.063.07819.212.81.122.29
Paolo Espino19867.51.294.51623.27.60.933.42
Randy Dobnak634.13.71.466.29816.17.21.7110.47
Ranger Suarez1265.28.91.081.512740.19.40.871.12
Reiss Knehr515.15.31.436.46713.27.21.543.29
Reynaldo Lopez937.181.134.11120.19.70.642.21
Riley Smith6252.91.767.921842.161.354.89
Ross Detwiler57.210.62.2215.264844.210.71.052.82
Ross Stripling1986.18.81.274.6951561.275.4
Ryan Weathers1869.16.51.536.361225.17.80.992.49
Ryan Yarbrough211176.71.265.469387.11.114.03
Sam Hentges12417.91.957.91827.210.41.524.88
Sammy Long522.19.31.214.43718.17.41.366.87
Sean Nolin517.28.21.75.65941.672
Spenser Watkins10466.31.677.6368.23.11.8510.38
Tanner Houck1358.211.21.133.68510.112.21.162.61
Taylor Hearn11516.51.295.823153.19.31.353.54
Taylor Widener13619.41.394.28109.18.71.824.82
Trevor Williams1568.28.81.514.33822.19.31.434.43
Tyler Alexander1566.271.223.382639.27.91.344.54
Wade LeBlanc937.15.11.584.34911.26.21.24.63
Zach Thompson1463.27.81.153.251211.18.71.593.18

Here are my thoughts on several of these pitchers (in alphabetical order by first and then last name, same as above).

Adbert Alzolay: A major split in talent from being a starter (17 K-BB%) and reliever (25 K-BB%). His walks jumped some (0.9 BB/9 to 2.7 BB/9) but remained reasonable. His main struggles stemmed from his HR/9 going from 0.5 to 2.0. He's basically just a two-pitch guy (fastball-slider) and therefore struggles each subsequent time through the batting order.

Role: K%-BB%

Reliever: 25%

1st TTO as SP: 21%

2nd TTO: 16%

3rd TTO: 10%

There is hope. He threw his changeup just seven percent of the time. The pitch had a 15 SwStr% and 52 GB%. It would be nice to see him bump its usage up to at least 20%. 

Cal Quantrill: I don't fully understand how he lowered his ERA from 4.32 (bullpen and few starts) to 1.94 ERA in the second half while throwing exclusively as a starter. All his ERA estimators remained around 4.00. His strikeout rate went from 6.3 K/9 to 8.0 K/9 as he threw his sinker (7 SwStr%, 50 GB%) fewer times (54% in April to 35% in September). He did move from a slider (14 SwStr%, 40 GB%) to a cutter (12 SwStr%, 39 GB%). While I believe he improved, the low ERA and WHIP (1.03 WHIP) were from a .240 BABIP and I'll bet on regression to the ERA estimators. 

Jose Suarez: While a .267 BABIP helped make his combined stats look acceptable (3.75 ERA, 1.23 WHIP and 7.8 K/9), he struggled when starting (4.44 ERA with matching ERA estimators). While he throws a bad curve and sinker, he's basically just a fastball-slider (20 SwStr%) guy. That combination works out of the bullpen. When he was forced to throw the sinker and curve, he struggled. His K-BB% dropped from 16% the first time through the order to 7% the second time, and 6% the third time. He is a perfect example of why it's important to split apart the starting and relieving results.

Keegan Thompson: I remember at one time last season having some interest in Thompson, but that quickly faded. Simply, I could not stomach a 1.48 WHIP coming from a 5.2 BB/9 (6.1 BB/9 as a starter). It was well above the 3.5 BB/9 (9 BB%) limit I set for pitchers. Additionally, his fastball lost over 2 mph when he transitioned to starting. If he ever starts throwing strikes... he had decent-enough results on his cutter (13 SwStr%, 50 GB%) and curve (14 SwStr%, 47 GB%) to take a step forward.

Randy Dobnak: I was a huge Dobnack fan coming into the 2021 season. He never struck out many batters (5.2 K/9 in 2020), but the lack of walks and an over 60 GB% were worth the risk. Instead, he focused on his sinker too much (44% to 59% usage) and had no swing-and-miss (3.7 K/9) as a starter. The groundball rate on all his pitches collapsed (sinker: 72% to 65%, slider: 58% to 36%, change: 46% to 27%) and the home runs soared (2.8 HR/9 as a reliever, 1.6 HR/9 as a starter). He has me thinking that a pitcher needs a base number of strikeouts to consider rostering. 

Ranger Suarez: What an amazing season, as both a starter and reliever after his average sinker velocity jumped from 91 mph to 93 mph. He had a 17.7 K-BB% as a starter and reliever. His ERA estimators are a bit higher near the mid-3.00s but still, a 3.50 ERA from a starter is acceptable. He was able to keep the home runs down with his high ground ball rate (64% as a reliever, 57% as a starter). Part of the drop was from throwing his four-seamer more (19% to 24%) with a 48 GB% versus 67% for his sinker. My one real question is if he can keep up his fastball velocity up since it dropped from 93.5 mph in August to 92.8 in September. 

Zach Thompson: He was able to keep a decent ERA in both roles (3.25 as a starter, 3.18 as a reliever), but his xFIPs (4.51 and 5.42) point to major regression. Now, he was better as a starter with his walk rate down at 3.1 BB/9 versus 4.8 BB/9 as a reliever. One major issue he faced was a drop in velocity after his first six starts (92.8 mph to 91.8 mph). Also, he kept messing with his pitch mix and should be able to get something to work with his curve (15 SwStr%, 50 GB%) and change (21 SwStr%, 52 GB%) being above average.  Keeping it simple, he's a nice sleeper if he could get his walk rate under 3.0 BB/9.

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ABOUT THE AUTHOR
Jeff Zimmerman
Zimmerman writes analytics-focused baseball and football articles for RotoWire. He is a three-time FSWA award winner, including the Football Writer of the Year and Best Football Print Article awards in 2016. The 2017 Tout Wars Mixed Auction champion and 2016 Tout Wars Head-to-Head champ, Zimmerman also contributes to FanGraphs.com, BaseballHQ and Baseball America.
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