By the end of last season, Major League Baseball saw a huge increase in home runs, and this season it has jumped again. Batters are hitting 1.16 home runs per game, the highest rate since 2000, widely considered the peak of its so-called Steroid Era. If this trend continues we will see close to 5,600 home runs hit, a huge spike after last year’s huge spike.
I looked into reasons why we have seen such a surge in home-run hitting before the season started, and ruled out as sole causes of climate change, improved scouting and even suggestions the ball itself was livelier. One possibility — one I hadn’t considered — was unearthed at this year’s All-Star Game when Baltimore Orioles catcher Matt Wieters floated his theory to Tyler Kepner of the New York Times.
“Secondary stuff isn’t as big of a thing as it used to be, I feel like,” Wieters said. “It’s now, ‘Can you throw 98, 99?’ And a lot of breaking balls that are hanging end up getting hit out.
“That’s my theory: The types of arms that are getting moved through the system are guys that can really throw hard, and command sometimes comes later for them. But they get to the big league level while they’re throwing hard, and then they learn command. Home runs, more times than not, are mistakes — they’re not the wrong pitch, they’re just mistakes in the middle of the plate.”
Wieters is correct: fastball velocity has been steadily on the rise. In 2002, the earliest data is available, fastballs averaged 89 mph, more than 3 mph fewer than this year’s average (92.2).
And there have been more home runs off pitches in the middle of the plate. According to MLB’s tracking data, there have been 522 home runs hit off 392,457 pitches down the center, a rate that would account for 110 more home runs than the year before.
But this still only accounts for a fraction of the approximately 700 extra home runs we are seeing this season. And command, at least in walks issued per game, had been improving until this season. For example, when last year’s home-run spike occurred, major league pitchers were walking 2.9 batters per game, the lowest rate in 50 years.
If we use strikeout-to-walk ratio as a proxy for command, that too was on the upswing. In 2015, pitchers struck out 2.7 batters for every one they walked compared to 1.7 in 2000. Looked at another way, this year’s 2.6 strikeout-to-walk ratio is virtually the same as it was in 2014 (2.7), yet there are 35 percent more home runs being hit.
And we aren’t seeing a huge influx of younger pitchers in the game, either. Per Baseball-Reference, the average pitcher age in 2000 was 28.8, just a few ticks higher than in 2016 (28.6).
The most likely answer continues to be a change in hitting philosophy, one that Jon Lester of the Chicago Cubs mentioned to Kepner on Monday night.
“I know our hitting coach wants you to hit the ball in the air,” Lester said. “There’s no slug on the ground. Guys are willing to take their punch-outs to hit the ball in the air, and swing hard in case they hit it.”
There are just two seasons of data to go on but according to MLB’s Statcast data, hitters had an average exit velocity of 88.5 mph coupled with an average launch angle of 10.5 degrees. Those have since risen to 89.2 and 11.3, respectively, in 2016. And this change in philosophy is affecting the younger generation more than ever. In 2013, hitters 25 years old or younger accounted for 20 percent of the total home runs hit, but now produce almost a quarter of all home runs.
In the end, it is a combination of things — park effects, influx of young talent, higher velocities, batter philosophies, etc. — acting in concert to send more baseballs out of the yard.