Felipe Rivero's changeup is phenomenal, but it can't help him retire lefties

Sabermetricians can't get enough of pitchers. We have data to prove it: In a March poll at FanGraphs, 43.6 percent of respondents described themselves as "pitcher dorks." Watching their throwing motions, #wanting their stuff, savoring the way they make hitters look silly — my, how we love those men on the mound. That means, like the pitchers themselves, we tend to dislike platoon splits. Even if a hurler has an untouchable pitch in his repertoire, it won't matter if he struggles against batters of a certain handedness.

Enter Nationals reliever Felipe Rivero. This year, he's displayed one of the scariest pitches in the majors (if you don't want it spoiled, ignore the title of this post). However, his failure with one type of split (which, again, you probably should just skip right down to the body) has prevented the 25-year-old lefty from becoming elite and from fully enjoying the fame that his dominant pitch would otherwise bring.

As a prospect, Rivero had a three-pitch arsenal, comprising a four-seam fastball, slider*, and changeup. The latter offering appeared to need some work: After the 2014 season, BP's Chris Crawford deemed it "viable," while FanGraphs' Kiley McDaniel said it "flash[ed] 55 but [was] more often a consistent 50." In his 2015 debut, Rivero unsurprisingly used the change just 4.7 percent of the time. On the strength of his heater/breaking ball combination, he compiled a 94 DRA- and 95 cFIP — respectably bland numbers from another faceless reliever.

*The scouting reports cited here call this a curveball, but I'll go with the Brooks Baseball classification.

In 2016, things have gone a little differently. I'll let Rivero's pitch frequency graph do the talking:

Rivero's quadrupled his changeup usage in 2016, and for good reason — not only has the pitch succeeded, it's dominated. 154 pitchers have thrown at least 100 changeups this season, and none of them has a better whiff rate on the pitch than Rivero:

Rivero's cambio hasn't been solely a swing-and-miss pitch. When put in play, it's stayed on the ground 54.6 percent of the time, placing a solid 54th in that sample. Those grounders haven't turned into hits, either: The changeup's .133 TAv against — about half of the .260 major-league baseline — ranks sixth. In every way imaginable, Rivero's changeup has smoked the competition.

So what makes the pitch so toxic? Let's watch him blow it past Juan Lagares:

Obviously, that velocity jumps out. Rivero has averaged 88.0 mph on the changeup this season, slotting him 15th in the majors. While that power certainly doesn't hurt, it doesn't mean a whole lot in and of itself. Rivero's fastball has gone toe-to-toe with his changeup, tallying an average velocity of 96.2 mph. According to my colleague Shawn Brody's research, the average pitcher has a 7.5-mph gap between his fastball and his changeup; Rivero hasn't diverged from this by much, meaning his changeup hasn't set itself apart with velocity alone.

What seems to accentuate the changeup's velocity is its scary movement. Notice how, despite standing pretty far toward first base — he's actually moved further left on the rubber this season — Rivero still sweeps his changeup across the plate. The pitch's 10.8 inches of horizontal movement, which only seven other pitchers have topped, help to make it a force. Lagares also appears to swing over the top of the pitch, probably because it's dipped more than the average changeup: Out of the 154-man sample, its vertical movement of 1.0 inches is the 14th-lowest.

That drop/run combination is quite rare, especially among southpaws. Here's a complete list of the left-handed pitchers who have thrown changeups with 10 or more inches of horizontal movement and two or fewer inches of vertical movement:

• Felipe Rivero (10.6 HMov, 1.0 VMov)
• Alex Claudio (12.2 HMov, -3.4 VMov)

Claudio's pitch isn't a changeup so much as an eephus — it's traveled at an average velocity of 68.1 mph this season. This really makes Rivero's changeup distinct: He's combined high-octane velocity with a devastating break, and his adversaries have been helpless.

Yet even with his changeup by his side, Rivero hasn't really stood out this season. He's certainly improved from 2015, but a 91 DRA- and 89 cFIP still won't attract much attention. The cause of his mediocrity? He's been downright awful when facing left-handed hitters, who have touched him up for a .399 wOBA in 2016. He's struck out half as many lefties (15.1 percent) as righties (32.3 percent) while walking a similar amount and giving up far more hard contact.

What's behind that reverse platoon split? Rivero has abandoned his most dangerous weapon versus same-handed opponents:

Rivero's pounded right-handed batters with the changeup, and it's pretty clearly paid off. The slider, on the other hand, has fallen short: As a whole, it has a middling 16.7 percent whiff rate, and hitters have a .210 TAv off it. Combine that with the fact that Rivero hasn't commanded his fastball against lefties — he's left the pitch up in the strike zone far too often, whereas he's tended to pitch around righties with it — and you get, essentially, a left-handed ROOGY.

It doesn't necessarily have to be this way. Max Marchi's timeless research on platoon splits showed that "power changeups" — i.e., the really fast ones — will generally work against batters of any handedness. Rivero currently has a 4.53 ERA after allowing runs in two of his last three appearances; at this point, maybe he should try experimenting with the changeup against lefties. It's either that, or developing a better slider or fastball. In a bullpen with emerging star Shawn Kelley, the Nationals don't need to rely on Rivero, which means he won't last very long if he doesn't perform.

In an ideal world, for Rivero and sabermetricians alike, the lefty would figure out some way to retire everyone. That way, we'd look at his changeup the same way that we view Dellin Betances's breaking ball or Andrew Miller's slider— as a truly otherworldly offering. Until then, though, he'll labor in anonymity, without a supporting cast of pitches to back up his changeup.

. . .

All statistics as of Saturday, July 30th.

Ryan Romano is a contributing editor for Beyond the Box Score. He also writes about the Orioles on Camden Depot and MASN Sports, and about the Brewers on BP Milwaukee.