If you thought the 2016 season had an unusually high number of homers, your eyes weren't lying to you: We saw 5,610 of them in 2016, far more than the 4,909 homers in 2015 and the 4,186 homers in 2014. A season full of home runs isn't the most unusual sight for a baseball fan, given that the home run rate was historically high in the era between 1994 and 2009.
We either grew up in a homer-centric game or spent a large chunk of our baseball lives watching balls clear fences, and pitchers kicking rosin bags or destroying Gatorade coolers in the dugout.
But 2016 was a surprise in that home runs jumped, with 3.04 percent of plate appearances ending in a home run. That's the most frequent rate in major league history, ahead of the 2000 season at 2.99 percent. And with 2016 having a much lower rate of other non-home run hits than at any time during the Home Run Era -- batters hit .270 overall in 2000 compared with .255 in 2016 -- the home run was a larger part of a team's offensive output than it ever had been.
Seasons with big home run spikes aren't always predictive of a new era, though. While the 1994 home run chases -- short-circuited by the strike -- did portend a new offensive environment, the original "Year of the Homer," the 1987 season, did not. For those who don't remember, the home run rate in baseball suddenly jumped nearly 20 percent that year, and players who had never hit home runs before were suddenly hitting a lot of them. Wade Boggs, an easy Hall of Famer but never a power hitter, hit 24 homers, 20 percent of his career total. The number of players who hit 30 home runs more than doubled, from 13 in 1986 to 28 in 1987.
Then a funny thing happened. The home runs stopped. It's not remembered these days, but the mini-era of 1988-1992 was a mini pitchers' era snuggled between years of digging the long ball. For example, in 1989, the AL scored only 4.29 runs a game. Knock off about 0.4 runs, the usual DH benefit or so, and only a few years in the late '60s and early '70s (1967, 1968, 1971, and 1972) featured less run-scoring. And remember, 1968 was the year Bob Gibson put up a 1.12 ERA. You'd have to go back to the dead ball era to find less offense.
Projecting 2017's level of offense is, by no means, an easy feat. The best predictor of a league's offense historically has been the average of recent seasons, but even that is not perfect. So ZiPS projected a level of home runs that was lower than that of 2016, and slightly higher than in the previous seasons.
But what if ZiPS' average of recent seasons is wrong? That we're without a clear and convincing reason why the homers suddenly came back doesn't mean that it won't happen again in 2017. From a projection standpoint, it does change things, simply because environmental changes don't have the same effect on every player and, therefore, every team.
A home run boost is better for the guys who hit homers than those who don't. A Mark Trumbo can add a lot more home runs than, say, Ben Revere, who probably would need the baseball to be made like a Super Ball to add a mass of home runs to his bottom line. A home run world favors those that have the skill set to hit home runs and those that can prevent others from doing so.
To see how it changed the projections for 2017, I re-ran the team-based simulations with a 14 percent increase in home runs from my baseline to see how it changed the standings from the last ZiPS run before the start of the season.
In the projections, the biggest beneficiaries of a 2016 home run level are the Colorado Rockies and the Baltimore Orioles. One of the reasons ZiPS liked the Rockies coming into the season is that there's a good chance they've finally assembled a group of pitchers that doesn't get destroyed by the long ball at Coors Field. Despite the home run explosion of last season, the Rockies' pitchers survived, allowing only 181 homers compared with the league average of 187, despite playing half their games in Coors Field. A pitching staff that can potentially survive Coors Field cares not for what league average is.
As for the O's, no team was more reliant on the home run in 2016. You might be under the impression that Baltimore had a world-class offense in 2016. It didn't. The team hit 253 home runs in 2016, 28 more than the next-best team in the majors (St. Louis at 225) and the fifth-most in MLB history. And all those home runs were needed just to get the Orioles to seventh in the AL in runs scored, at 744.
On the flip side, 2016-level homer-hitting hurts teams such as the Giants and Pirates, who don't have offenses or parks that can take advantage of the round-tripper. The Pirates, in particular, gave up an above-average number of homers overall, and the Giants weren't that much better than average once you factor in the pitcher-friendly confines of AT&T Park.
And what about Seattle? You wouldn't think, initially, that the Mariners would suffer as much, given that they finished second in the AL with 223 home runs hit, but they also allowed 213 homers, the third-most in the American League. While ZiPS projects the Mariners overall will be as solid as they were in 2016, the computer expects them to be overall less dependent on the home runs, with Nelson Cruz and Robinson Cano well into their 30s and fairly one-dimensional sluggers such as Adam Lind and Dae-Ho Lee departed.
Unfortunately, we won't really know what 2017 is like until we get further into the season. (Which is too bad -- ZiPS projections would be scary accurate if I could run them for 2017 after the season!) In the first two days (Opening Day, versions 1.0 and 2.0), 3.1 percent of plate appearances have resulted in home runs in 2017, and that's with the league's best starters taking the hill. That's based on one game of baseball from 28 teams and none from the remaining two, so if I took that too seriously, the "Small Sample Size Police" would come and throw me into a dark oubliette found under Bill James's house and throw away the key.
But whether 2016 was a mirage or a trend that could have a significant impact on the 2017 standings is something we'll keep an eye on.