The Mets’ 2020 bullpen and the Edwin Diaz dilemma

According FanGraphs’ Steamer system, the 2020 New York Mets are projected to have the top bullpen in the National League and the third-best relief corps in all of baseball with an even 5.0 fWAR. That’s a seemingly preposterous notion to a fan base that suffered through a season sunk by what was, for large parts of the year, a historically bad bullpen. If your immediate reaction was to scoff at the absurdity of it all, you’re not alone.

Still, it was easy to be fairly high on the Mets’ relievers heading into the 2019 season. The team traded for dominant closer Edwin Diaz, re-signed formerly dominant closer Jeurys Familia, and added Justin Wilson to a bullpen that already included stud Seth Lugo and the (usually) dependable Robert Gsellman. It looked pretty good on paper, anyway.

There were plenty of reasons that last season’s bullpen was such a disaster. Injury, poor performance, lack of depth, bad bullpen management, lack of starter length early in the season, and plain bad luck are just a few that can reasonably be applied to the 2019 Mets’ beleaguered bullpen. Perhaps the singular most relevant reason for the collapse, however, is also a most clichéd baseball adage: bullpens are volatile.

First-year general manager Brodie Van Wagenen looked to make a splash in a now infamous move that traded some of the Mets’ future for win-now reliever Diaz and win-yesterday second baseman Robinson Cano. It’s hard to imagine how the trade could have turned out any worse considering both players flopped, but the floundering Diaz will likely have the bigger impact on the success (or failure) of the 2020 Mets.

By now you’ve seen multiple analyses that center on Diaz’s poor 2019 performance from the outcome perspective (increased HR rate, walks, etc.), and we’ll definitely touch on that a bit further in this article. As a change of pace, though, this piece focuses more on the execution and behavior of his pitches in an attempt to identify any key differences between 2018 and 2019 that may have led to such contrasting results.

There’s understandably been a lot of chatter about his slider and its ineffectiveness this past season, but his fastball was noticeably worse in 2019 as well. You’d be hard-pressed to find a more striking example of the consequences of a two-pitch reliever losing both of his weapons, and the situation was made all the worse for Diaz as a newly-acquired, high-profile player in the New York market.

The table below presents various data points pertaining to Diaz’s arsenal (his four-seam fastball and slider) for both 2018 and 2019. The information is sourced from Statcast and Pitch/FX data from multiple sites, including FanGraphs, Baseball Savant, and Brooks Baseball. I’ve also included a scatter plot from Brooks Baseball below the table that depicts the average movement of his pitches in 2018 and 2019. This is in an effort to provide a bit more context for the positive and negative numbers associated with pitch movement and release points, and there’s a short primer at the end of this article providing additional detail*.

2019 FS 2018 FS 2019 SL 2018 SL
Spin Rate 2371 2341 2367 2377
H-Move(in) -7.04 -5.96 0.97 1.17
V-Move(in) 7.91 8.9 2.72 2.4
Velo 97.8 97.9 89.8 89.7
V-Release(ft) 5.14 5.31 5.35 5.45
H-Release(ft) -2.93 -2.76 -2.85 -2.7
HardHitRate 47.50% 36.90% 42.60% 32.70%
FB% 30.77% 26.19% 29.79% 18.75%
HR 9 2 6 3
BAA .237 .188 .333 .121
K% 41.50% 32.90% 35.90% 56.40%

The first things to note are that the spin rate on his four-seamer ticked up by 30rpm and both the horizontal and vertical movement changed fairly significantly. That 30rpm may seem insignificant, but keep in mind that even a difference of 100rpm at high velocities can impact swinging strike percentages significantly. Oddly, the upward vertical movement on his four-seamer actually decreased rather than increased with the higher spin rate. You’d typically see the reverse, where more backspin leads to an increase in the “rise” of a four-seam fastball. There’s a difference of a full inch here, which is considerable for a game where mere millimeters mean the difference between a home run and a pop fly. The change in horizontal movement on his fastball also indicates an increase in sidespin, causing it to cut more into right-handers and away from lefties. These differences could indicate a slight change in his grip, where the pitch acts a bit more like a two-seamer but is still clearly a four-seam fastball.

It’s likely that his slower slider wasn’t affected as much by the smaller 10rpm decrease in spin rate, though with this pitch its horizontal movement would be impacted more by changes in the spin rate. We can see that there’s less than an inch of difference in vertical and horizontal movement on the pitch between 2018 and 2019, though it’s worth pointing out that it had more lift and less break away from right-handers than it did in 2018. Again, small differences can have huge consequences.

The changes in the release point for both pitches were included in the table because it’s an interesting data point, and I thought perhaps inconsistencies here may have been a potential cause of his bad fortune. Though he had a slightly lower, flatter release point for both pitches in 2019, it really is negligible. As an aside, I plotted both pitches by month for 2018 and 2019 in the charts below, and he’s actually been remarkably consistent.

So what does all of this get us besides a closer look at some cool Statcast and Pitch/FX data? Well, at the very least we can see that some of his mechanics have remained consistent between 2018 and 2019. It’s a bit of a stretch to believe that the slight changes in the behavior of his pitches led to the carnage that was his 2019 in Queens, but hitters were clearly locked in when he took the mound. This is evidenced by the sample of outcome metrics in the table that really drive home just how thoroughly Diaz was thrashed last season.

The hard hit rate for each of his pitches in 2019 was astronomical and averaged out to 45.3%, which was in the bottom 2% of the MLB. Statcast also has a statistic known as Barrel, which essentially leverages exit velocity and launch angle to identify how many times a batter “squares up” on a pitch. Unsurprisingly, Diaz’s 10.1 Barrel% was in the bottom 8% of the MLB last season. The huge increases in his fly ball rate, home runs allowed, and batting average against are well known at this point, but they’re quite stark when compared to the small changes in his pitch behavior.

If we consider that his 2019 pitches acted very similarly to their 2018 counterparts, and there was no dip in velocity, then we’re left with questions centered on things like his ability to hit his location, pitch tipping, sequencing, and just plain bad luck.

It’s difficult to analyze differences in the sequencing of his pitches and the predictability of the choices he and his battery mate made in any given at bat, though it should be noted that he only leaned on his four-seamer slightly more often in 2019 than he did the season before. Likewise, and while still a possibility, it would be surprising if he was tipping his pitches and we have yet to hear about it. Still, the authority with which hitters demolished his offerings and the roughly 10% increase in their pull rate against him sure make it seem like they had a good idea of what was coming. In terms of luck, attributing his ills to the cruel fates certainly seems like a cop out, but the .377 BABIP that hitters tallied against him combined with the almost 10% increase in contact on his pitches outside the zone sort of bear that line of thinking out a bit.

What does Diaz need to fix and how does he do it? Is there actually something that needs fixing? It may be that the Mets eventually do identify the cause for his down year and he makes the appropriate corrections heading in 2020, but it’s possible that we already identified the primary cause many paragraphs ago. Relievers are a fickle bunch, and it’s perfectly reasonable to believe that Diaz had a 58-inning blip that was more catastrophic to his team’s fortunes than most sample sizes that small.

Returning to the premise of our headline, the dilemma the Mets are presented with is whether or not to hand Diaz the closer role at the outset of the 2020 season and make it his to lose. With a year in the New York spotlight under his belt, and the hope for a regression to the mean regarding luck, do they bank on him getting back on course as the anchor for what has the potential to be an elite bullpen? Or do they hand the reins to someone like Lugo and make Diaz earn it back like he did in Seattle in 2017? For what it’s worth, I’m of the opinion that you plug Diaz in as the closer and remove him if he once again plays himself out of that role. Only, you know, do it sooner.

It might be hyperbolic to state that the success of the Mets’ 2020 bullpen depends on which version of Diaz manifests itself next season, but it’s not that far from the truth. As we saw this past season, it only takes one failing cog to throw the entire machine into disarray. A healthy and effective quartet of Lugo, Familia, Diaz, and the newly-acquired Dellin Betances could certainly make that projection a reality, but there are many “ifs” involved in reaching that ideal scenario. Can Diaz and Familia regain their form? Will a healthy Betances come close to resembling his former, dominant self? Will the time bomb that is Lugo’s elbow continue to hold up?

That 5.0 fWAR projection would absolutely look nice on the Mets’ bullpen this season, but before we start counting those chickens we should remember that Steamer was pretty high on the Mets’ bullpen in 2019 as well. What did the projection gods foresee before last season for Mets relief pitchers? Second in the NL and third in the MLB with an fWAR of 4.3. Of course, they just missed the mark on that one by landing at a robust 0.7 fWAR. Relievers, man.

* The X and Y axes intersect at the center with a value of zero. The perspective is from the catcher’s point of view with the intersection acting as the center of home plate. Negative numbers on the Y-axis represent downward movement, while positive numbers represent upward movement. Likewise, negative numbers on the X-axis represent pitches moving towards a right-handed batter while positive numbers represent pitches moving away. The locations of the bubbles are relative to the center of the chart and do not represent where the pitches landed within the strike zone.

7 comments for “The Mets’ 2020 bullpen and the Edwin Diaz dilemma

  1. TexasGusCC
    January 25, 2020 at 10:01 am

    Rob, great stuff. A few things caught my attention:

    – After seeing the Hard Hit Rates of 2018, I went to check on four other pitchers for reference (Lugo, Gsellman, DeGrom, K. Jansen) and all of them had HH% in the low 30’s and Jansen went to 37% last year. I would not have traded for a pitcher with rates in the upper 30’s.

    – Can you explain how a difference in RPMs affects a pitch? My point is that revolutions per minute sound great, but a baseball gets to the plate at about 0.4 seconds. That makes it 150 times faster than on a “per minute” basis, so those gaudy 2,700 rpm numbers we see need to be divided by 150. That gives Diaz 18 revolutions before it gets to the plate. Since the seams we’re lowered last year, it’s expected in just 18 spins the ball would move less than previously.

    – Pitch tipping may come from many areas. If a catcher sets up too quickly to catch a hard fastball; if a pitcher holds his glove in different positions depending on his next pitch; or as simple as he has a shorter set for fastballs than he has for sliders. Supposedly, they were “making adjustments” continuously last year, and that was from a seasoned pitching coach as the manager two long and longer pitching gurus as the pitching coach. A first time ever manager teamed up with a first time ever pitching coach, makes for a bad marriage to help these guys catch some of this stuff.

    • Barry
      January 25, 2020 at 10:47 am

      I thought all along that he was tipping his pitches. Remember, in the beginning of the year he was pitching ok. Not as dominant as 2018, but still nothing to complain about.

      I think the reason they wanted Beltran was because of his savant-like ability to figure out how a pitcher is tipping his pitches. This isn’t sarcasm and I’m not referring to cheating. He was great at the “legal” side of tipping pitches.

      If this is true, I just hope he had enough time with Diaz in Port St. Lucie to “fix” him. I wanted Girardi, but I thought if Beltran could fix Diaz, it would be well worth it; so I was bummed out that Beltran had to go.

    • January 25, 2020 at 11:52 am

      Thanks, Gus!

      The short answer is that the spin rate relates to the amount of force the ball exerts against the air around it, and how that air in turn affects the movement of the ball via counter pressure.

      The long answer is best answered by folks much smarter than me. Please see this link and its second part here. It’s all very interesting.

  2. January 25, 2020 at 11:25 am

    Great stuff, Rob.

    I felt like his slider was the problem last year. I’m surprised the difference in horizontal break wasn’t greater but I really have no point of comparison. Maybe that’s a huge difference and I just don’t recognize it. Or maybe the difference got greater after the first six-eight weeks of the season.

    My opinion is that you have to start the year with Lugo as the closer. If on Opening Day, deGrom goes 8 innings and there’s a one-run lead in the 9th, I want to see Lugo come in.

    But, with the club’s hesitancy to use Lugo on back-to-back days – especially early in the year – you would figure there would be some save opportunities available for Diaz.

    • Boomboom
      January 25, 2020 at 1:10 pm

      Slider was definitely an issue but i think the fact he had trouble (my perception) locating his fastball was more problematic. How many guys did he nearly kill high inside? I can remember at least 3 vividly including 2 pitches in a row against the white sox. I think that takes a mental toll on the pitcher and makes him less committed to the pitch. Self perpetuating problem then.

  3. Metsense
    January 25, 2020 at 12:19 pm

    Intricate and interesting stuff in the article.
    Bullpen management is difficult and can make or break a manager. A good starting rotation that produces quality starts helps. Over used of a relief pitcher should be avoided. Constant pitching changes matchups, which burn out a bullpen, should be remedied by the rule change. Rojas and Hefner, although inexperienced, have the knowledge and analytics to run a bullpen. All they need to do is implement their convictions. Easier said than done.
    Diaz would not be my closer when the season start. In fact, he would initially be behind Lugo, Betances, Wilson and Brach. The Mets should used Lugo as their primary closer. He earned it. Diaz has the talent the rise up in the pecking order but he has to earn it. The bullpen has enough talent and experience to step in when Lugo is unavailable.

  4. TJ
    January 25, 2020 at 8:48 pm

    Rob,
    Great stuff, thanks for the efforts.

    Metsense,
    Agree 100%, and I like Rojas’s non-commital better than Beltran’s view on Diaz. And ditto Familia. I think both can regain their effectiveness, but the have to prove it and earn those late innings.

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