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Looking at the inconsistencies of hard-hit rate

Something was wrong with the metric in 2018...

Los Angeles Angels of Anaheim v Houston Astros Photo by Bob Levey/Getty Images

Kole Calhoun had an odd season. For the most part, minus a second-half surge, he was pretty terrible. He put up career lows in batting average, BABIP, on-base percentage, and slugging percentage. But standing with all those low marks was a career-high. A significant career-high. Calhoun posted a hard-hit rate of 44.5 percent, considerably above his previous high of 35.3 percent and even more above his career-rate of 33.7 percent.

So with better quality of contact he’s ever put up in a season, why did Calhoun see such a dip in offensive production? He did see a slight decrease in his plate discipline metrics, but that doesn’t seem like enough of an answer for such a huge decline.

Now this article isn’t some deep dive on Kole Calhoun. It’s a look at the bigger picture, because upon further review, their were more cases like Calhoun in the 2018 season. Players that increased their quality of contact by measurable standards but saw an overall decline in offensive production—Tommy Pham, Mike Moustakas, and Starlin Castro, to name a few.

If you’re a frequent lurker on the depths of the FanGraphs leaderboards, you’ll know there was something up with hard-hit rate in the league as a whole. The league rate reached a season-high (35.3 percent) in Baseball Info Solution’s record history of the metric.

Back over at RotoGraphs in July, Alex Chamberlain did an examination on the funky trends of batted-ball statistics in 2018, mainly looking at hard-hit rate and xwOBA.

“That’s kind of a big deal. It doesn’t mean you should dismiss hard-hit rate as a usable metric; it still very much is. And you should still celebrate hitters who improve their hard-hit rate year over year. It’s just that gains are substantially less meaningful in 2018 — and losses are all the more detrimental. What’s important to note is Hard% isn’t broken. It has peaked in 2018 just as exit velocity and barrels and ideal hits have all peaked. From where I’m sitting, it is still characterizing contact quality commensurate with Statcast’s raw and stylized measurements of contact quality.”

Chamberlain pointed it out astutely with his conclusion of the meaning of hard-hit rate. It’s still an important and useful statistic. But it meant a whole lot less in 2018. Using data from when the metric’s tracking started (2002), I found the year-to-year changes of two statistics for every player with at least 200 plate appearances in consecutive seasons (2004 to 2005, 2009 to 2010, 2017 to 2018, etc). The two stats I looked at were hard-hit rate and wOBA, simply measuring year-to-year changes in quality of contact and offensive production.

The findings fit all the previous hypothesis. A change in hard-hit rate meant less than ever did (well at least in its recorded history) in 2018. Taking every player’s change in wOBA and hard-hit rate and adding/matching them up, I found the correlation numbers for each season between the two.

The correlation reached a low between the 2017 and 2017 seasons, a mark only comparable to the correlation between the 2004 and 2005 seasons. As for theories regarding the cause, two main ideas popped into my head.

  1. Defensive shifts reached an all-time impact in 2018, turning more hard-hit batted balls into outs
  2. The tinkering of the baseball is messing with the batted ball tracking, a theory brought up much in recent years. Hard-hit rate is devised from an algorithm that takes factors like batted ball type, distance, and hang time into account, so possibly the physics of the changing ball have messed with this algorithm. Just speculation and maybe a project for another day.

None of this analysis is meant to deter the great work of those at Baseball Info Solutions that track statistics like this. Hard-hit rate is still an incredibly useful stat with the right time and place. It’s just the recent inconsistencies with metric should be taken into consideration when citing it.


Patrick Brennan loves to research pitchers and minor leaguers with data. You can find additional work of his at Royals Review and Royals Farm Report. You can also find him on Twitter @paintingcorner.