Fantasy Baseball: Advanced stats primer for hitters

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Last week, we received this email from a Fantasy Baseball Today podcast listener:

"Hey guys. When you're using advanced stats in player discussions is there any way you could list other players with similar profiles for context? I personally feel like this will help translate what advanced stat profiles actually could mean for production. Thank you."

This is something we'll get every once in a while, and it's a fair request. Not everyone is up to date on the latest minutiae from around the  baseball world, and all of these alphabet soup stats we throw at you can probably start to sound like nonsense at some point.  

So, I took some time to compile a few of my most-cited advanced stats, with an explanation for what they measure, how to use them, and a bit of context for what their results might mean. If you have any other questions, please don't hesitate to email FantasyBaseball@CBSi.com so we can help.

BABIP

What does it mean? Batting Average on Balls In Play. It measures a hitter's success rate when taking strikeouts and home runs out of the question. We'll reference this one a lot. 

Why does it matter? Generally speaking, there's a lot of noise around batting average, and BABIP represents where most of that noise comes from. Hitters have some control over their BABIP — hitting line drives, hitting the ball the opposite way, and being fast are three ways batters can control it — but a lot of it is luck. The league tends to aggregate around .300 BABIP, and the majority of hitters are going to be within 30 points of that one way or the other. Anything much higher or lower than that can typically be chalked up to luck, good or bad. Random variation around BABIP can often help explain outlier performances. 

Some key results from 2018:

It's not all luck, of course. Kipnis' BABIP has been in the .260 range two consecutive years, and his increased infield fly ball rate is a good sign that there's a deterioration in skill here. You do want to try to figure out a player's baseline expectation first and foremost, because a.351 BABIP by Brandon Nimmo isn't the same as one from Christian Yelich. 

Where can you find it? FanGraphs.com has it on every player's page, along with yearly and career leaderboards. 

BB%

What does it mean? Walks divided by plate appearances. About as straightforward as you can get. 

Why does it matter? Getting on base is important, and walking is one of the best ways to do that. It's important to use rate stats rather than counting stats, to adjust for playing time, too. 

Some key results from 2018: 

This matters a bit less for Rotisserie scoring, where OBP isn't a direct scoring category. However, for H2H points, you'll want to give guys with a high walk rate a boost. 

Where can you find it? FanGraphs.com has it on player pages. Or, you can just use a calculator. 

K%

What does it mean? Strikeouts divided by plate appearances. Walk rate's cousin. 

Why does it matter? Strikeouts aren't that much worse than regular outs, but they do represent a lost opportunity for production. A batted ball, even one weakly struck, can still turn into a hit. Not so for strikeouts. The more a player strikeouts out, the less likely they are to hit for average and produce counting stats — though if they do enough else well, they can still be very valuable. Just ask Aaron Judge. 

Key results from 2018:

As you can see, strikeout rate on its own might not tell you much. On one end of the extreme, we have a bad hitter; on the other end, a bad hitter. Ideally, you want a player who avoids strikeouts at a high rate, which is why guys like Alex Bregman and Jose Altuve are so valuable. However, it shouldn't be a big part of your analysis on its own, unless you're looking for reasons why it might change in the future. That's where you'll use some of the pitch-level data we'll get into shortly.

Where can you find it: FanGraphs.com or a calculator, again. 

ISO  

What does it mean? Isolated slugging percentage. Literally just slugging percentage minus batting average. 

Why does it matter? We tend to think about power in terms of homers, but home runs can fluctuate quite bit from year to year, while ISO takes into account doubles and triples, so a bad luck season won't necessarily look as bad here. 

Key results from 2018:

This one doesn't need a lot of thinking over. Good power hitters hit for a lot of power. It is interesting to note here Harper's elite ISO in 2018, widely considered to be a disappointing season. A lot of his apparent struggles in 2018 (though not all!) came about because of a .289 BABIP, compared to a .319 career mark. 

Where can you find it? FanGraphs.com. Or, again, a calculator.

HR/FB

What does it mean? Home runs divided by fly balls. 

Why does it matter? Because home runs are relatively rare events, even for big time power hitters, luck can still play a pretty significant part in season-long homer totals. Great power hitters will sport high HR/FB rates, and it tracks pretty well with hard-hit%, a solid stand-in for raw power. Which makes intuitive sense: Players with more raw power should be expected to see more of their  fly balls leave the park. Because they are hitting them harder. 

Key results from 2018:

We're starting to get away from more "luck"-based stats, because hitters really do have quite a bit of control over their HR/FB rate. However, there is still plenty of fluctuation from one year to the next. For example, while there's no doubting Cody Bellinger's raw power, he saw his HR/FB rate fall from 25.2% to 15.2% from 2017 to 2018; in that same time, his hard-hit rate remained largely unchained. At least some of his struggles last year can be chalked up to some bad luck.

Where can you find it? FanGraphs.com. 

LD%

What does it mean? Line drive percentage. The share of all batted balls classified as line drives (by Baseball Info Solutions' tracking).

Why does it matter? There is a reasonably strong relationship between line drive rate and BABIP. It's not perfect — a higher line drive rate doesn't explain all of the variation in BABIP. But it gets us part of the way to explaining why some players can have more success on balls in play than others. 

Key results from 2018:

Ironically, these three examples illustrate the limitations of using line drive rate to explain BABIP. All three of these hitters clustered right around average in 2018 in BABIP, despite the wide variance in LD%. That highlights one limitation of LD%: It's not terribly predictable year to year. It is a measure of how well a hitter hit the ball in any given year, but it doesn't always carry over from last year. It's a useful thing to know, but you shouldn't rely on it too much. 

Where can I find it? FanGraphs.com

GB%

What does it mean? Groundball rate. Share of batted balls hit on the ground.

Why does it matter? Production doesn't live on the ground. You can get a single, maybe an occasional double or triple, on a ground ball. But unless the defense just trips all over themselves over and over, you aren't getting home on the ground. And with teams getting better and more aggressive with their usage of shifts, groundballs are becoming less and less desirable each year. 

Key results from 2018:

Mauer is a great example of a player whose value was hurt tremendously by the increase in shifting. His batted ball profile was just too predictable: If he hit it on the ground, it was almost certainly going to the right side; if it was in the air, it was going to the opposite field. Some players want to hit the ball on the ground more, like Dee Gordon or Mallex Smith, but that's as much about their lack of raw power as it is about anything else. All other things being equal, you probably want fewer groundballs. 

Where can you find it? FanGraphs.com

FB%

What does it mean? Flyball rate. Share of batted balls that are fly balls. 

Why does it matter? This is where power lives. You'll get the occasional line drive homer, but for the most part, home runs come from fly balls. The more fly balls you hit, the more chances you have for home runs. It doesn't mean it will always lead to more home runs, of course — there's that inherent volatility of HR/FB rate to contend with, as well as the possibility of  more  infield fly balls, an issue for Bellinger last season, for one. 

Key results from 2018:

Tommy Pham hits the ball hard consistently, but there's a pretty hard cap on how many home runs you can expect from him, given his extreme groundball tendencies. Rosario and Gennett are two players who have seen their performance improve alongside an increase in flyball rate, and the "flyball revolution" has largely been driven by the understanding that more balls  in the air generally means better production. Ryan Braun is one example of a player early this season enjoying success after adjusting his swing. 

Where can you find it: Fangraphs.com

Also: You can use average launch angle as another proxy for these batted-ball numbers. The higher the average launch angle, the more balls that player is hitting in the air. Braun's has jumped from 5.8% to nearly 12% in the early going this season. 

Hard%

What does it mean? Share of batted balls rated "soft contact" by Baseball Info Solutions (it's a proprietary metric, so we don't know exactly how they define it). 

Why does it matter? As I said earlier, it's a good proxy for raw power. Generally speaking, the more often you hit the ball hard, the more often the ball will go out of the yard. An increase in hard-hit% is usually a good sign that a power breakout is real — or is imminent. 

Key results from 2018:

That mostly fits. Peraza  isn't a bad hitter, but he is a prototypical slap hitter. Nimmo was a solid source of power in 2018, but shouldn't be expected to be a 30-homer hitter anytime soon. Mauer sticks out like a sore thumb here, but his directional batted-ball profile explains some of why this didn't manifest in much power, because of his easily-shiftable tendencies. 

Where you can find it: FanGraphs.com

Soft%

What does it mean? How often the hitter hits the ball "soft."

Why does it matter? Less important than hard-hit percentage, but still useful to look at. Less for  what it means on its own, than for what  it can represent about a player's consistency, or lack thereof. Hitting the ball hard is great, but avoiding hitting the ball poorly can be what separates the good from the great — and the perpetually inconsistent and frustrating from both of  them. 

Key results from 2018:

Marte has started to show some power, but you can see how inconsistency remains an issue for him. Marte may have decent raw power, but avoiding the  lows is still the key to him taking a leap. 

Where you can find it: FanGraphs.com.

Contact%

What does it mean? How often a hitter makes contact when he swings

Why does it matter? Contact skills still matter in 2019. In fact, they may matter more than ever, given how rampant swings-and-misses are today. If you can put the bat on the ball, you have a chance to be a standout.

Key results from 2018:

Of course, this doesn't tell us anything about quality of contact. Putting the bat on the ball consistently isn't enough to make a player Fantasy relevant by itself. The more useful way to use Contact% is by looking at year-over-year trends. For example: Joey Gallo's 65.2 percent contact rate is still really bad, but it represents a third consecutive season of improvement. If he can keep that up, this strong start may not be a fluke. 

Where you can find it: FanGraphs.com.  

Avg. Exit Velocity

What does it mean? How hard the ball comes off a hitter's bat, on average.

Why does it matter? Well, that's obvious, isn't it? It's both a more and less refined version of hard-hit%. On the one hand, you're not dealing with hazily defined markers like "hard" or "soft," which can paint a more accurate picture. On the other hand, while hard/soft% take into account where the ball was hit, this treats flyballs, line drives, and groundballs the same. 

Key results from 2018:

These results shouldn't be a surprise. Average exit velocity is important, but it's not everything. One cool thing about BaseballSavant.com's StatCast data is, it also breaks up average exit velocity by line drives/flyballs and groundballs. If you're wondering why someone who hits the ball hard consistently might not  be getting the kind of power production you might hope for, it might be that they tend to hit the ball harder on the ground, which isn't going to lead to power. 

Where can you find it? BaseballSavant.com

Barrels

What does it mean? It's sort of convoluted, so I'll let MLB.com explain it: 

Why does it matter? Barreled balls are usually going to lead to good results for a hitter. It's not just that he hit the ball hard, but that he hit it hard at a launch angle that typically leads to extra bases. 

Key results from 2018:

You can sort by both "barrels/batted ball event" and "barrels/PA,"  but the latter is the default. Cron's 2018 breakout is backed up by this measure, at least. Generally speaking, Barrel rate is a good proxy for overall hitting ability, but because they are relatively rare events in and of themselves, they don't necessarily account for consistency. So, a player might have a high barrel rate, but still be a frustrating hitter, because he might hit an equal number of pop ups, or weak grounders. 

Where can you find it? BaseballSavant.com  

One additional neat thing BaseballSavant.com has for their batted ball data are their "expected stats," which try to give hitters credit for the quality of their contact, regardless of the outcomes. It isn't super predictive or sticky year over year, but it's interesting to look and see who might have had a bit of bad or good luck impact their results. 

Sprint Speed

What does it mean? How fast a player runs the bases.

Why does it matter? Because it tells you fast a player runs the bases. It's pretty straightforward. 

Key results from 2018:

Absolutely no surprises here: Slow guys are slow, fast guys are fast. This is a skill that can be pretty directly expressed. One thing this could be useful for is identifying potential stolen base breakouts. As my colleague Scott White often says, stolen bases are about intent. But having the underlying skill doesn't hurt either. 

Where can you find it? BaseballSavant.com