The Sustainability of Robert Stephenson’s Success

After starting off the season with an abysmal 1-8 record, the Cincinnati Reds have won seven of their last twelve contests. Nonetheless, they’re last place in the NL Central division, trailing the first place Pirates by five games. Their offense has been very poor (3.4 runs/game), but the pitching has been great (team ERA in the low 3s). One reliever who has been integral to their bullpen’s success is Robert Stephenson.

Stephenson, a former 1st round pick out of Alhambra (CA) HS in 2011, spent four full seasons in the minors before receiving his first taste of the big leagues in 2016. He put up a 6.08 ERA in 37 innings, alarmingly walking over 4.5 batters per nine innings. The following season was met with mixed results. Robert Stephenson dropped his ERA to 4.68, but his control regressed (walked over 5.5 batters per nine innings). In 2018, Stephenson pitched exceptionally well at AAA (2.87 ERA, 10.75 K/9, and 4.54 BB/9 in 113 IP); however, he did not impress one bit in his limited major league action (8.49 K/9, 9.26 BB/9, and 9.26 ERA). Among the 618 pitchers who pitched at least 10 innings in 2018, only three of them walked over nine batters per nine innings, with Stephenson being one of them.

This year has been another story. Stephenson has walked just two batters in 11.1 innings pitched. He has whiffed nearly 40% of the hitters he’s faced (12.71 K/9), he’s yet to concede a HR, and his ERA is excellent (1.59 ERA). Additionally, Stephenson has been worth 0.5 fWAR, which is the highest among all members of the Reds bullpen. He has seemingly overcome the shoulder inflammation he dealt with early on in ST…

“Stephenson, who dealt with shoulder inflammation at the beginning of the spring, changed the grip on his fastball and feels a lot more comfortable throwing it. He’s faced 32 batters this season and walked one – an issue that troubled him for years.” – Bobby Nightengale, Cincinnati Enquirer.

There are many underlying reasons that could explain why Stephenson is having more success…

1. Increased Fastball Velocity

Pitch Info Pitch Velocity readings (as found on FanGraphs)

2018 FB velocity – 93.8

2018 FB SwStr% – 3.3

2018 AVG against – .526


2019 FB velocity – 94.9 (+1.1)

2019 FB SwStr% – 5.9

2019 AVG against – .333 (-.193)

2. Pitching Solely in Relief

Career AVG against 1st time through the order (all stats per FanGraphs unless otherwise noted) – .236

Career ERA 1st time through the order – 3.48


Career AVG against 2nd time through the order – .272

Career ERA 2nd time through the order – 5.27


Career AVG against 3rd time through the order – .276

Career ERA 3rd time through the order – 6.53

3. More Sliders

2018 Pitch Mix and SwStr%

FB: 36.4%; 3.3

CH: 18.2%; 13.3

SL: 40.1%; 18.2

CB: 5.3%; 7.7


2019 Pitch Mix and SwStr%

FB: 35.9% (-0.5); 5.9

CH: 5.6% (-12.6); 12.5

SL: 57.0% (+16.9); 33.3

CB: 0.7% (-4.6); 0.0 (*only 1 CB thrown)

4. Increased Slider Spin

Graph via Baseball Savant

More spin (presumably) correlates to more movement, which has transformed Stephenson’s slider into one of the most lethal pitches in the MLB. Once again hitters, are whiffing at 1/3 of the sliders they see from Stephenson. That is an unprecedented rate…

Near the end of the 2018 regular season, we polled 85 big leaguers (both hitters and pitchers) from 28 clubs with that exact question. And we put particular emphasis on the “right now,” because this conversation is always evolving.Anthony Castrovince of

Chris Sale’s slider was voted the most nasty pitch (16 votes); its SwStr% in 2018 was 16.8, and hitters managed a .113 AVG against it. 

Robert Stephenson has thrown 81 sliders this year. He’s conceded only two hits (.087 AVG)! Obviously, the sample size is small, but one cannot help but get excited about what Stephenson has been able to accomplish thus far in 2019. 

Graph via Brooks Baseball

Altering his horizontal release point may have contributed to increased spin on his slider.

5. Slider Location

Graph via Brooks Baseball

On average, Robert Stephenson has located his slider lower than last year. This likely makes it more challenging for the hitter to barrel up the pitch…

Graph via Baseball Savant

As depicted in the graph above, hitters are having a much harder time squaring up the ball this season compared to last year.

Stephenson’s success early on appears to be sustainable. If he can stay healthy, look for him to continue to grow as a pitcher and to be called upon in more high leverage situations. 

Featured Photo:Kareem Elgazzar/The Enquirer

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