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Ariel Miranda is showing why BABIP isn’t just about luck

Despite having the league’s lowest BABIP, Ariel Miranda is struggling.

Los Angeles Angels of Anaheim v Seattle Mariners Photo by Stephen Brashear/Getty Images

One of the first advanced statistics most people become familiar with is batting average on balls in play, or BABIP. It’s simple enough, taking the most widely used of all baseball stats — batting average — and eliminating any instance in which the defense played no role in an outcome (strikeouts, walks, and home runs, mostly). Because of what it entails and its simplicity, BABIP has become somewhat synonymous with luck. It’s easy to explain away a player’s poor performance by looking at their BABIP and proclaiming, “oh, they’re just getting unlucky.” Too low means their balls are finding more mitts than usual; too high means they’re getting more seeing-eye singles than normal. But treating BABIP as synonymous with luck is a mistake. Case in point: Mariners starter Ariel Miranda.

Over the past two seasons Miranda has a BABIP of .224, which represents the lowest number in baseball among pitchers who have thrown at least 120 innings — a group of 183 starters and high-usage, multi-inning relievers.* That fact on it’s own is only kind of interesting. What makes it compelling is that Miranda’s other numbers over that period haven’t been great, even though he gets way more outs on balls in play than is normal. You would expect a pitcher with a BABIP that low to be dominant, but despite how difficult it has been for opposing hitters to find success on the balls they put in play, Miranda has struggled. Here’s a breakdown comparing some notable statistics from his 2016 and 2017 seasons.

(*) Note: He also has the lowest BABIP if the threshold is 100 innings, but I wanted to eliminate most of the single-inning relievers from the leaderboard, since they are often brought into the game with favorable matchups.

Ariel Miranda 2016 vs. 2017

Season IP K% BB% BABIP LOB% LD% GB% FB% IFFB% HR/FB ERA FIP
Season IP K% BB% BABIP LOB% LD% GB% FB% IFFB% HR/FB ERA FIP
2016 58 19.0% 7.8% .222 76.8% 17.6% 31.2% 51.2% 16.1% 13.8% 3.88 5.25
2017 115 18.7% 8.3% .226 76.8% 15.9% 33.2% 50.9% 12.9% 12.9% 4.30 5.18
Data via FanGraphs

While his 3.88 ERA in 2016 told the story of a solid pitcher, his 5.25 FIP begged to differ. This season, Miranda’s FIP has remained almost identical at 5.18, but his ERA has risen to 4.35. What stands out overall is how consistent the numbers have been between the two seasons. The most drastic change for Miranda came in his aforementioned ERA increase, but nearly everything else is stable. He’s maintained a walk rate right around league average, and his strikeout rate remains below. Miranda’s left-on-base percentage is literally identical, for crying out loud. This southpaw has been a model of consistency.

So why has Miranda’s BABIP been the best in baseball and yet his results mediocre at best? While BABIP can absolutely point us in the direction of unusual amounts of luck, it has to be examined in the context of the other aspects of their batted ball profile. In Miranda’s case, take a look at his fly ball rates. Among that same sample of pitchers with a minimum of 120 innings pitched since 2016, he has paired the lowest BABIP with the highest fly ball rate — 51 percent. Here’s one of those fun scatter plots with a ridiculous outlier to drive this fact home. Miranda is in the top left corner, all alone and marked in red.

Here we have Ariel Miranda’s mark doing it’s best impression of me at a party with people I don’t know.
Data via FanGraphs

This helps to explain why, despite being the BABIP king, Miranda isn’t a dominant force. A little more than half of all the balls put into play against him are fly balls, and while fly balls turn into outs more often than grounders, they usually result in extra bases when they aren’t caught. And some of those extra-base hits — the home runs — don’t count against BABIP. While Miranda’s 12.9 percent home-run-to-fly-ball rate is below the league average mark of 13.7 percent, since he’s a fly ball pitcher by nature, even a league average rate means he’s going to give up a lot of long balls. Miranda has given up 22 home runs in 2017, tied for sixth in all of baseball.

While his rate stats have stayed consistent from 2016 to 2017, the type of home runs Miranda has allowed help to explain part of the difference in his ERA between the two seasons. Last year, 83 percent of the dingers Miranda gave up were solo blasts. This year? Just 59 percent of opposing home runs have come with the bases empty. If we were to hypothetically make 83 percent of his 2017 home runs solo, that would take six runs of off his total runs allowed and his ERA would be 3.86, almost exactly what it was last season. Miranda has been the model of consistency, but he’s seen more long balls this year come at inopportune times with men on base, and his ERA has suffered the consequences.

The nature of Miranda’s fly ball tendencies mean that when he gets burned, it’s likely to be by a home run, which explains why his FIP has been worse than his ERA in both of his major league seasons. FIP looks at only the metrics that a pitcher has the most control over — strikeouts, walks, and home runs — while Miranda’s low BABIP is due in part to factors beyond his control. His fly ball tendencies are all his own, but he pitches in a pitcher’s park with an outfield defense that ranks second in baseball with 24 defensive runs saved in 2017. (Seattle’s outfield defense in 2016 was not good, but Miranda’s thrown two-thirds of his career innings this season.)

BABIP can be an incredibly informative statistic, but it must be paired with context regarding a player’s batted ball tendencies. Ariel Miranda has carried the league’s lowest BABIP since for the past two seasons, but that doesn’t mean he’s been lucky. That’s just who he is: an extreme flyball pitcher, with all the fly outs and dingers that entails.


Chris Anders is a featured writer at Beyond the Box Score. You can find him on Twitter @MrChrisAnders.