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The Seranthony Dominguez Problem

After a torrid start to his career in relief, the rookie has fallen on hard times. Is it a passing phase?

MLB: Los Angeles Dodgers at Philadelphia Phillies Bill Streicher-USA TODAY Sports

Seranthony Dominguez’s first 12 career appearances will go down as the stuff of legend. The 23-year-old former starter, having ascended through the minor leagues with more helium than your typical child’s birthday party, immediately began looking as if this job was the easiest one in the world. Over those 12 appearances, Dominguez would only allow two hits, walk none, and strike out 16 of the 46 batters he faced. Better yet: The Phillies were 11-1 in those games, from May 7 to June 5 (they went 3-10 in the other games during that stretch).

No one could have been certain that what has happened since was inevitable. Even as Dominguez’s 13th game yielded his first struggles and eventually ended in Jason Heyward hitting a walk-off grand slam against Adam Morgan, and his 14th saw the Brewers score a run against him in his second inning of work, there wasn’t really a reason to lose much confidence. That was two games versus 13, and two games against really good offenses, at that. So he was mortal, so what?

At the All-Star break, Dominguez had pitched in 28 Major League games, plus 11 with Reading and Lehigh Valley. With the big club, his numbers were stifling:

  • 33.2 innings in those 28 games
  • 43 strikeouts and 6 walks in 124 batters faced
  • 1.60 ERA
  • An insane .139/.194/.191 opponents’ slash

You were watching. You remember.

Since the All-Star break ended, though, things have been different. Among the numerous problems facing this freefalling club, Dominguez has begun to look more than merely mortal: He’s looked like a rookie. He’s still getting his strikeouts, if for no other reason than his raw stuff remains too damn nasty not to, but nothing else has been clicking.

  • 11 innings in 13 games
  • 14 strikeouts and 8 walks in 53 batters faced
  • 8.18 ERA
  • A Rhys Hoskins-esque .256/.396/.535 opponents’ slash

But again, you were watching. You remember.

So, while that’s obviously not great, those numbers themselves don’t point toward a cause or justification for why things have gone south for Seranthony. There’s a perfectly logical assumption to be made that he could be tiring; he’s appeared in more than 50 games across the Majors and minors this year, far surpassing his career high of just 17 total appearances, and is approaching a new career high in innings (60.1, high of 76).

Seeing as that’s not an apples-to-apples comparison from starting to relieving, there are questions we can’t necessarily answer right now about the toll the different work schedule is taking on Dominguez. We just can’t. You have to prepare and warm up differently, you throw harder in every appearance, you have some back-to-backs. It’s just a different beast. How Seranthony is responding to the demands of this year will tell us a lot, both about where he is as a Major Leaguer now and how far he has yet to go to withstand a full season in the bullpen.

Let’s look a bit deeper into Seranthony’s stuff and results.

One of the very first things I like to look for when checking into reliever struggles is velocity. It’s rarely ever a great thing when a pitcher’s velocity drops midseason, whatever the actual cause ends up being. Is that a red flag for Dominguez?


Nothing doing, there. The fastball’s come down a little, but the slider’s gained. He’s still throwing hard. How about the spin of those pitches, for kicks?


Apart from one weird dip in slider spin from May*, no, everything looks fine there, too.

* That was May 26 against Toronto. He threw two sliders, one to Luke Maile and one to Curtis Granderson. The one to Granderson was a little sloppy, but otherwise this just looks like a blip.

And his release points, are they holding up? Take a look at a chart of his release points from his appearance in game 2 of the Mets doubleheader last week and Saturday’s performance.

August 16
August 25

There’s a clear loosening charted here, but we can’t really draw a correlation. Look at the charts below, showing Dominguez’s release point spread in his last five appearances.


Saturday’s is the ugliest, but it doesn’t stray too far from the cluster in the Boston appearance on August 15, where Seranthony didn’t register a strikeout but retired all four batters faced. Even comparing it to the chart of one of his most dominant appearances, May 28 against the Dodgers, you can see that a spread does not tie directly into ineffectiveness. Nothing looks alarming.

May 28

So, let’s say the stuff and mechanics are fine.

What else can we look at? Sequencing and approach.

As the season has progressed. some of Seranthony’s patterns have become clearer. One that stands out is that, to-date, he has not thrown a single changeup to a right-handed hitter. Understanding that, right-handed hitters can focus a bit more on fastballs. Dominguez’s response to that is to use his two-seamer more against righties, trying to use that same arm-side movement a changeup would provide, but running it in on the hands quicker than a changeup would. Seems like a pretty sound strategy.

It’s pretty clearly not a pitch he trusts to use other than in spots where he has wiggle room ahead in a count, at least not yet. Now, as batters become more accustomed to the cut on Seranthony’s fastball, they’re able to lay off more and pick better pitches to swing at. Right-handed hitters just aren’t missing the heater like they were earlier in the summer.


In response, slider usage has ticked up.


The slider still comes in very hard, at 88-90 MPH, and right-handed hitters can’t do a thing with it. Statcast data says right-handed hitters have struck out 19 times on sliders, put 16 of them in play, and have zero hits to show for it. Ze-ro. So, that adjustment is working.

It’s not effective against lefties, though, and that’s a problem. In fact, on August 5 and 6, Dominguez threw two sliders to left-handed batters: Justin Bour and David Peralta. Both hit them for home runs, and none of the 44 pitches to a left-handed batter since has been a slider. We may see a bit more of a lean toward the changeup - four of them came on Saturday alone - as long as the slider remains weak against lefties.

But what if the biggest culprit is something much simpler?

In the first half, 45 of the 124 batters Dominguez faced went ahead 1-0. Another 17 put the first pitch in play. Add in one first-pitch HBP, and we find remaining 61 hitters started 0-1. In the second half, that advantage has disappeared: 27 of 53 hitters have started 1-0.

You know what I’m about to show you next.

Seranthony Dominguez, 0-1 vs. 1-0

Season, After 1-0 73 .210 .329 .339 20 11
Season, After 0-1 92 .153 .207 .259 37 3

Dominguez is so, so much better when he works from a count advantage. Even as he’s cut back on the walks in August - just one in his eight appearances - he’s still allowing opponents to OPS a crazy 1.073. The 10 hits he’s allowed have gone as follows:

  1. Derek Dietrich - Started 1-0, Ended 2-2, Double
  2. Justin Bour - Started 1-0, Ended 1-1, Home Run
  3. David Peralta - Started 0-1, Ended 0-1, Home Run
  4. Eduardo Escobar - Started 1-0, Ended 3-2, Double
  5. Steven Souza - Started 0-1, Ended 3-2, Single
  6. Cory Spangenberg - Started 0-1, Ended 0-1, Single
  7. Wilmer Flores - Started 1-0, Ended 2-0, Single
  8. Juan Soto - Started 0-1, Ended 2-2, Double
  9. Ryan Zimmerman - Started 1-0, Ended 2-1, Home Run
  10. Kendrys Morales - Started 0-1, Ended 1-2, Single

So, it’s just been that kind of stretch. Even when he gets ahead, he’s still getting burned sometimes. But it does highlight how low the “After 0-1” numbers were before that stretch of three singles, a double, and a home run, sprinkled in among the outs.

Anyway, there’s nothing really groundbreaking happening here. The Phillies have a pitcher with relief ace-type stuff who’s stuck in a rut. Some of his weaknesses - sliders to lefties, falling behind in counts - have come to the forefront as he continues to navigate his rookie year. He doesn’t appear hurt, and he’s mostly recovered from the rather extreme control issues that besieged him at the start of the second half.

What he’ll need to do is continue to refine his command on the first pitch. It’s not a mandate that you get ahead 0-1 at all costs, because that’s how you develop a habit of throwing meatballs, but it’s evident that Seranthony and his wicked stuff play up further still when the hitter’s back on his heels. Right now, he’s working from behind too much, but that’s more easily fixed than any potential injury or burnout situation. It’s a bummer that his struggles have come at such key moments for this team, but it’s far from signaling an impending collapse.