Gary Sanchez has a .197 batting average on balls in play (BABIP), the second-lowest of any qualified hitter this year. That's actually understating it, to some extent; that .197 mark would be the lowest BABIP of any qualified Yankees hitter in the last century. It's a big part of why Sanchez is currently hitting a disappointing .190/.291/.430 after going 0-for-4 in the Yankees' 2-0 loss to the Mets on Sunday.
Because it strips out strikeouts and home runs, BABIP exists to tell the story of only what happens when the ball is put into play, on only those plate appearances where a fielder can make an impact. While a batter has a great deal of control over his own walks, strikeouts and home runs, he has only partial control over the outcomes of balls in play. As such, BABIP has long been used to determine good or bad "luck" for those hitters who have abnormally high or low marks.
Sometimes it tells a story. As in, sometimes a low BABIP really does mean poor fortune. But it's dangerous to look at a low mark and instantly assume that's the case, because depending on the situation, a low BABIP can actually be telling you any number of stories.
So what does it mean for Sanchez? And what does it tell us about how the rest of his season may play out?
Let's look at five possible reasons that he's not finding success when he puts the ball in play, then explain what the real reason likely is.
1) Maybe he's not hitting the ball hard.
The first thing you think of when you see a low BABIP is simply "lousy contact." It's nice to avoid strikeouts and put the bat on the ball, but it doesn't really matter much if it's weak contact. That's what is happening to Kansas City's Alcides Escobar, for example. He has a .236 BABIP, well below the Major League average of .294. In his case, it's not likely to be bad luck, because he has a hard-hit rate of just 24.9 percent, also well below the league average of 36.3 percent. Poor contact leads to poor outcomes.
However, that doesn't seem to be Sanchez's problem. Last year, when he hit .278/.345/.531 with 33 home runs, he had a 43.1 percent hard-hit rate and a 90.8-mph average exit velocity, both strong marks. While struggling this year, he has a 41.7 percent hard-hit rate and a 89.8-mph exit velocity. Those are down from last year, but only slightly, and are still above average. His hard-hit rate is better than Eric Hosmer or Matt Kemp, just to name a few. This is mostly not the issue.

2) Maybe it's because he's not fast.
Sanchez, a catcher, isn't known for his foot speed. Statcast™ has a metric called sprint speed, which measures a runner's top speed in feet per second, and Sanchez ranks 366th of 445 qualified players, or slower than about 82 percent of hitters. As you'd expect, there's some relationship between speed and BABIP, because fast players can beat out infield hits and slow ones rarely do.
Then again, Sanchez wasn't exactly speedy when he had a .307 BABIP from 2015-17, either. It's probably not this, at least not more than it has ever been.
3) Maybe he's getting eaten up by the shift.
While the shift may have less impact than we think it does, one thing it does do effectively is turn likely singles into outs. Obviously, hard-hit balls that would have been a hit in years past often now turn into outs, thanks to a well-positioned fielder.
Though this mostly affects lefty batters, Sanchez is getting shifted more, 40 percent of the time this year, up from 28 percent last year. But he has a .269 BABIP against the shift, and a .160 mark when he's not being shifted. It's probably not this, either.
4) Maybe it's just bad luck.
This is the most popular reason for a low BABIP, and it's often true. We've all seen poorly hit bloops turn into doubles or crushed line drives find gloves. That's just the way baseball works, and it's why batting lines and actual skills don't always have a perfect correlation.
Just look at how Sunday night's game ended. Sanchez hit a hard line drive, one that had a 61 percent hit probability (based on exit velocity and launch angle, but because it was right at third baseman Todd Frazier, it turned into a game-ending double play.

There's probably a little truth to this. Sanchez's expected BABIP, again based on likely outcomes of his exit velocity and launch angle, is .265, a 67-point difference from his actual .198 BABIP. Out of 224 hitters with 100 balls in play, that gap is the 17th-largest. Out of 123 right-handed hitters, it's the fifth-largest gap. It's probably fair to say that some of Sanchez's issues are hard-hit balls hit right to waiting gloves.
5) Maybe the BABIP is skewed because it doesn't count homers.
Sometimes, BABIP doesn't mean what you think it does at all. If you take the "in play" aspect to an extreme, the second-lowest BABIP in Yankees history belongs to Roger Maris (.209) in his historic 61-homer 1961 season. It can be hard to put up a good batting average on balls in play when your 61 best hits don't count as "in play." It's probably not this, either. But it's worth noting, because Sanchez does have 12 homers, tied for the most of any catcher.
So it's not any of that, at least not as a primary factor. So what is it? What's happening with Sanchez?
Well, it might be simple. When Sanchez hits the ball in the air, he does it very well. When he hits it on the ground, he does it worse than almost anyone.
There have been 232 players who have hit at least 50 fly balls and line drives this year, and on those balls, Sanchez has been elite. He has a 98.7-mph exit velocity, which ranks fourth behind Joey Gallo, Giancarlo Stanton and J.D. Martinez. On those non-homer batted balls in play, he has a .412 BABIP, a little above the league average (.398).
Meanwhile, there have been 199 players with at least 50 ground balls. On those, Sanchez has been mediocre. His exit velocity is 84.5 mph, which is 137th, or lower than about two-thirds of players, including noted non-sluggers Orlando Arcia and Ian Desmond. His BABIP on grounders is .082, which is 199th. That's the worst in baseball. He has put 61 grounders in play, and has hits on just five of them.

Put it all together, and there's no player in baseball with a larger difference between their grounders and hits in the air. There have been 186 hitters with 50 grounders and 50 flies/liners, and Sanchez's difference of 14.2 mph between his strong 98.7-mph exit velocity on balls in the air and his weak 84.5-mph grounder exit velocity is the largest. The 333-point difference between his .082 grounder BABIP and his .412 liner/fly ball BABIP is the third-largest.
There are a lot of factors at play in Sanchez's disappointing 2018, really. He's striking out a little more, but he's walking a lot more. His popup rate has jumped from 10 percent to 14 percent, and popups are basically free outs. He's been wildly streaky, hitting .056/.081/.167 in his first nine games, then a very strong .288/.394/.676 over his next 30 starts, then a miserable .075/.197/.094 in 15 games since.
There's a lot happening here. But a big part of it is that when Sanchez puts the ball in play, he's not getting the results he'd expect. It's a little about poor fortune. It's a lot about the fact that ground balls are just about the worst thing a slow-footed catcher with elite power can do. After all, weakly hit ground balls from a player without speed are unlikely to end well. For Sanchez, that's true to an extreme so far.