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With a baseball offseason filled with tense CBA negotiations, prospect lists injecting much-needed optimism, and the perpetual warmth of the sizzling hot stove transaction season underway, the fantasy team at Baseball Prospectus is launching its second annual “Fantasy Categorical Breakdown” series. This is the first installment of our category-by-category review, which will feature a look at the general landscape, over and under-achievers and a deeper dive, to provide fantasy owners with a distinct advantage heading into 2017.

“In the big leagues, they don’t pay you for ground balls, they pay you for doubles and home runs.” Josh Donaldson on MLB Network

Major-league hitters produced the second-most home runs in baseball history this past season. The unprecedented home run surge, which began with a statistically significant uptick during the second half of the 2015 campaign evolved into arguably the most polarizing and hotly debated topic industry-wide for one simple reason. We don’t really have a solid explanation. Why are there more home runs than at any point in nearly two decades?

As Jeff Sullivan wrote in an essay entitled “Return of the Run” in the Hardball Times Baseball Annual this past offseason, “It’s a difficult question to answer. Maybe that’s surprising to you; maybe it isn’t. I talked to a handful of front office members, and they couldn’t offer anything definitive. There are some theories, and some partial explanations, but it’s hard to get all the way there.”

Reality is infinitely complex. It’s difficult to explain how veteran starter James Shields served up 40 dingers all by himself in 2016. For the record, that’s more than reliever Luke Gregerson has allowed (39) in his entire eight-year career dating back to 2009. Before we dive into the research, some potential explanations, and the fantasy ramifications of the home run deluge, let’s begin with a look at the raw data.

Home Runs on Contact 2002-2016

Contact Rate 2002-2016

From a fantasy perspective, the single biggest takeaway from these two graphs, using data from Baseball-Reference, is that hitters are making quite a bit less contact in recent years, but they have essentially begun to maximize the value of each batted ball when they do connect, clearing the fences at a dramatically higher rate.

Power is cyclical. It ebbs and flows over lengthy periods without swinging too far in one direction. However, home runs on contact, where contact is defined as at-bats plus sacrifice flies minus strikeouts, declined steadily for nearly decade before bottoming out completely by the end of 2014. Former BP authors Rob Arthur and Ben Lindbergh effectively summarized why at FiveThirtyEight earlier this year, “Over the previous several seasons, scoring in baseball had dropped to levels not seen since the mid-1970s, as an expanded strike zone, an increase in average pitch velocity, the rise of defensive shifts, and detailed data on batter tendencies had combined to keep runs scarce.”

Clearly, home runs on contact have rebounded at an unheard of rate over the past two seasons. Fantasy owners need to adjust their expectations in terms of projecting players future performance in the power department and how a league-wide uptick impacts the value of home runs moving forward. An elite power hitter capable of racking up 35 home runs is worth less in the current offensive environment than he would have been for fantasy owners just two years ago. Striking that correct balance between under and over-reacting to recent evidence is difficult under the best of circumstances, but it’s exponentially more difficult when we don’t have a concrete explanation for why more baseballs are going home as souvenirs.

Are The Baseballs Juiced?

As Sullivan noted later in the same Hardball Times Baseball Annual piece, one entirely possible explanation is randomness. “Sometimes things just happen, without rhyme or reason, because ultimately we’re dealing with samples of data. It’s possible the effect could be nothing.” I find it completely acceptable to settle on randomness as a plausible explanation for Philadelphia’s Freddy Galvis, a 26-year-old second baseman known primarily for his defensive prowess, slugging 20 home runs completely out of left field in 2016. That’s fine. However, there seems to be compelling evidence that this isn’t a random development.

One of the foremost experts on the physics of baseball, Alan Nathan, a professor emeritus of physics at the University of Illinois concluded though his research in an article for The Hardball Times in July that, “the principal factor accounting for the large increase in home runs in 2016 is likely due to exit speed.” Nathan wouldn’t go as far as to speculate whether it was caused by “juiced baseballs” he later revisited the data and highlighted that while there was a clear increase in mean exit speed for launch angles in the home run sweet spot, 20-to-35 degrees, mean exit speeds were essentially identical for line-drive angles ranging from, zero-to-10 degrees. According to Nathan, this isn’t what you would expect to find if the baseballs were “juiced”. Still, we can’t dismiss the juiced ball theory entirely.

Arthur and Lindbergh became the most notable voices on the subject with their data-driven columns throughout the season and it’s hard to dismiss their case. Especially the data comparing major-league and minor-league home run rates. Just like Fox Mulder on The X-Files, I want to believe.

Let’s Do Launch…Angle

One factor that we haven’t considered yet is the potential impact of a broader, fundamental change in approach by hitters during the last few seasons. It’s something that Tom Tango, an icon in the sabermetric community and author of “The Book: Playing the Percentages in Baseball” hired by MLB Advanced Media as their Senior Database Architect of Stats this summer, outlined in a recent blog post. According to Tango, hitters appear to be changing the way they are approaching each plate appearance by focusing on lofting the ball whenever they make contact, and placing an increased emphasis on their launch angle. It’s yet another factor to consider and while it doesn’t apply to every hitter in the game, there are some prominent examples. Most notable among them is Donaldson, the reigning AL MVP.

In a conversation with former major leaguer Mark DeRosa, the Blue Jays slugger takes a deep dive into the mechanics of his swing, one predicated on hitting the ball in the air and generating plenty of loft. It would be gross oversimplification to suggest that all hitters are modeling their approach Donaldson, but for a fringe major-league talent, it might not be a bad strategy.

It’s an extreme example, but take a look at someone like Ryan Schimpf. He made his major-league debut at 28-years-old this past year after seven-plus seasons in the minor leagues. Of the 60 hits the LSU product racked up over 330 plate appearances, only 18 were singles. The rest, including 20 home runs, went for extra-bases. Per Baseball Savant, Schimpf recorded the highest average launch angle (27.7 degrees) of any major-league hitter with at least 100-batted balls recorded by Statcast. His average launch angle was more than five degrees higher than any other hitter this past season. His batted ball profile, featuring a 65 percent fly ball rate and 15 percent infield pop-up percent, is truly absurd. We haven’t even mentioned that he struck out in nearly 32 percent of his plate appearances. Still, his season will be viewed on a surface level as an overall success solely because he hit for a ton of power in limited playing time.

This isn’t meant to be an indictment on Schimpf. Even the “worst” major leaguers are among the 1000 or so best in the world at their profession, but even with superb power production in limited playing time, he accounted for just three (2.9) wins above replacement in 330 plate appearances. Given the extreme volatility associated with his batted ball profile, approach at the plate, and below-average fielding, it’s unlikely that he develops into a one of the elite position players in the game anytime soon. Still, he had a tremendous impact for his fantasy owners, supplying home runs at the keystone off the waiver wire.

Schimpf is a prime example of hitters at the bottom of the major-league talent pool clearing the fences with a higher frequency, benefiting the most from the rise in exit velocity, and emphasis on improving launch angles over the last year and a half, thus contributing more to the league-wide surge than established power hitters adding to their already prodigious totals.

The data seems to back up that specific hypothesis. Here is a look at the number of individual hitters that have eclipsed the 35, 25, and 10-home run plateaus every year dating back to 2002.

Year

10+ HR

20+ HR

35+ HR

2002

188

81

15

2003

206

86

19

2004

207

93

20

2005

195

78

14

2006

202

91

23

2007

201

86

8

2008

186

92

11

2009

198

87

13

2010

176

77

6

2011

176

68

8

2012

188

79

9

2013

194

70

5

2014

163

57

7

2015

199

64

15

2016

214

111

17

Nearly twice as many hitters joined the 20-home run club than the previous year, and the most of any single season in the last decade and a half. Over the last three years, elder statesmen David Ortiz and Nelson Cruz are the only hitters to blast 35-plus home runs in every season. The fact that elite sluggers didn’t experience a dramatic increase over that same span relative to historical averages in the sample suggests that we shouldn’t expect their production to increase in the future. The hitters who stand to benefit the most from increased exit velocity and better launch angles are ones, like Galvis and Schimpf, guys that fantasy owners least expect.

Where Do We Go Now?

Forecasting future events, even ones that will transpire in just a few months, is incredibly difficult. It’s almost impossible to determine whether the recent home run surge over the last two years is a harbinger of things to come or if it’s a random outlier due for regression towards power outputs more in line with the pre-Statcast era.

While it’s important to acknowledge the limits of our predictive power, it would be foolish to dismiss all prediction as an exercise in futility. Based on all of the compelling evidence, fantasy owners should account for the recent events impacting home run production. It’s critical to adjust our benchmarks for elite power hitters and recognize that the fantasy value of these sluggers declining as production in the category is likely to emerge from a variety of exciting new spots on our fantasy rosters moving forward.

Thank you for reading

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DrDaley
11/14
Perhaps the warmer weather....or could it be the Election Cycle Effect. Note HR's went up across the board in each national election yr, except one ( 2008) and that was only in the first category. This year blame Trump!!
GeorgeBissell
11/14
Alan Nathan addressed the potential impact of global warming in a guest piece here at BP back in 2012. He found through his research that a one-degree climb in average temperature would increase home-run rate by less than one percent. So temperature wouldn't be a driving force when it comes to increasing home run totals. You can read the entire piece here: http://www.baseballprospectus.com/article.php?articleid=17249
yibberat
11/16
I looked at some data (HR increase by actual position played) and about 2/3 of the increase in HR's came from three positions (2B, SS, CF) that have historically lived/died on speed instead. So my hypothesis is that the decline in stolen base opportunities (and also the higher turnover in those positions to younger generation of players who are more homer-happy) is the driving force behind the increase in HR's. The more marginal speedsters just aren't going to get the green lights anymore. So they adjusted their plate approach to get more loft (and reduce the chances that they just end up on 1B with no chance to steal second). And that resulted in increased HR's. If that's true, I would also expect their HR's to regress a lot this year. I also think that pitchers have probably pitched those batters differently in the past (expecting more contact and less power). They got surprised - and they will adjust.
GeorgeBissell
11/16
The variables impacting the league-wide decline in stolen bases is something my BP colleague Rob Mains has written about often this year. Simply put, teams are getting smarter, being more selective about when they send runners, mitigating the risk of getting thrown out and trying to prevent injuries to key players sliding into bases. I touched on "fringe major-league hitters" quite a bit in the piece and that they are the ones who seem to benefit the most from the statistically significant league-wide uptick in exit velocity over the last year and a half. I would agree that there is an emphasis being placed on putting the ball in the air, increasing hitters launch angles, to maximize the value of each batted ball in an era where strikeouts are up and contact is way down. It's entirely possible that home runs could experience a regression toward the mean, more in line with historical averages. However, given that this recent trend began in the second half of 2015 and carried over into 2016, I wouldn't expect power to decline to the depths of 2014 anytime soon. Appreciate the insightful comment.