2019’s Quietest Breakout

The 2019 Reds were an enigma. They had the firepower, led by the homer-happy Eugenio Suarez. They had the rookie sensation, Aristides Aquino, who dingered like it was nobody’s business. On the pitching side, they had a steady crop of reliable pitchers. Sonny Gray was the unquestionable ace of the staff while the quartet of Raisel Iglesias, Michael Lorenzen, Amir Garrett, and Robert Stephenson anchored the pen. Despite all that, they finished with a lowly 75-87 record, 16 games behind the first-place Cardinals.

Going into 2019, no one would have guessed how pivotal of a role Stephenson, 26, would have played. He came into the year with a career 5.47 ERA, a 5.50 FIP, and a 1.673 WHIP over the past three seasons. His career was clearly at a crossroads; He was a former top prospect who hadn’t shown sustained success at the major-league level. He spent much of 2018 in the minors, regaining his mojo, pitching to a 2.87 ERA in 20 starts with the Louisville Bats, Cincinnati’s Triple-A affiliate.

The Reds announced at the end of spring training that Stephenson would start 2019 out of the bullpen. Since Stephenson was out of options, this year was most likely the last chance he would get in Cincinnati. It became a make-or-break, sink-or-swim, pitch-well-or-ya-gone type of campaign. Despite all of the stress and lack of previous MLB success, Stephenson engineered one of the most unheard and unlikely breakout seasons in 2019.

His Baseball Savant page is a thing of beauty. His xBA, xSLG, hard-hit percentage, and xwOBA all rank in the top 5% of all pitchers in 2019, while his strikeout percentage, fastball velocity, and exit velocity against placed him in or over the 25th percentile.

His 2019 season trended positively in many ways. He cut down on his walks, his strikeout percentage increased almost 10 percent, and his exit velocity decreased by almost 2 mph. Additionally, his barrel percentage dropped five percentage points, his swinging-strike rate fell by over seven points, and his overall whiff percentage skyrocketed 14% up to 39%. Using Statcast’s player similarity chart, his 2019 campaign was most comparable to Kenley Jansen’s 2019. That’s pretty good company to be in.

At a time when everyone’s pining for relievers that throw more than one inning at a time, he had multi-inning appearances 16 times, a stat surely aided by the fact that he’s had plenty of experience hurling multiple frames as a starter.

Upon Stephenson’s full-time move to the bullpen, his fastball notched up a tick velocity-wise, but the batters kept on squaring it up (.416 xwOBA). Stephenson reverted to his slider as his main pitch, and for good reason. It was his bread and butter, ranking as one of the most effective pitches in the majors.

His change in pitch selection was a huge factor in his breakout 2019 campaign. Stephenson’s slider ranked as one of the most effective pitches in baseball last year. When he ended an at-bat with it, it resulted in a .193 xwOBA and a 52.2 whiff percentage. His slider averaged 2799 RPMs, the 10th-best mark in baseball. His 16.6 slider value (wSL) ranked the pitch as the most effective slider among relievers in 2019, more than two points above the second-highest finisher (Will Smith, 14.2).

What makes his slider so unhittable is its location. Looking at his pitch location chart, Stephenson typically buries his slider in the lower third of the batter’s box. Its horizontal movement was an inch above league-average while its vertical movement was four inches lower than the MLB average, placing him 33rd among all pitchers in vertical drop in 2019.

However, if you just look at his rate stats, it doesn’t really show an effective season. His ERA was 3.76 (84 ERA-) and his fly-ball and HR/9 rate sits comfortably above the league average. So why did his underlying stats paint him in a much better picture than his rate stats?

The most likely explanation lies in the physical composition of the baseball itself. Many have speculated, and rightly so, that the baseball has been “juiced” in 2019, which has led to exit velocity and launch angle numbers skyrocketing. Many pitchers have complained of the difference of the new ball, claiming that it affects the break of their pitches. While Stephenson has not publicly lamented about any issues, it’s clear the new ball’s been negatively impacting him. 

Compared to 2017 (his last full season spent in the Majors), his launch angle rose 5.7 degrees, his fly-ball percentage rose 5.2%, and his HR/FB soared to 12.7%. With Major League Baseball expected to potentially dumb-down the ball in 2020, Stephenson seems like he could be a prime rebound candidate.

Stephenson may be ready to emerge as the next great reliever for Cincinnati, and with the Reds creeping more towards contention, you could be hearing his name a lot more in the future.