Home Runs are Down; Home Runs are More Important Than Ever

marc w · April 12, 2018 at 5:03 pm · Filed Under Mariners 

A couple of weeks ago, I appended some guesses (“projections,” excuse me) to the opening day game post. Like so much of what I write here, they have fared poorly in their initial skirmishes with reality. Key among my assumptions – and it really felt more like an assumption rather than a projection – was that HRs would continue to rise. It’s very, very early, but HRs, as described in this Athletic piece by Rob Arthur ($), have dropped fairly dramatically. First, oops. Second, what?

The first thing that jumps off the page in the early-season league-wide stats is just how *well* batters are hitting the ball. Ground ball rate is down by over a full percentage point from last April, and 1.7 percentage points from April 2016. The drop in batting average on balls in play we’ve seen over the past few years has continued, but it’s not reflected in Statcast measures like average exit velocity. Both exit velocity AND launch angle are up, not down, and they’re up fairly substantially. In April of last year, a year when the ball was flying over the fence at unprecedented rates, the average exit velocity for all contact was 86.7 MPH. This year, it’s 88.2 MPH. If we focus just on the *best* contact, the combination of angle and velocity that’s most likely to turn into HRs and extra-base hits – the contact Statcast calls “barrels” – there’s never been more of it. The percentage of pitches that were “barreled” last year was 1.09%, essentially the same as 2016’s 1.11%. In the early going in 2018, that figure is 1.29%.

What’s changed is the value of a barrel. In 2016, about 57% of barrels flew over the fence as homers. In 2017, that went up to about 62%. In the first week or two this year, that figure has cratered to 46%. All of this has Statcast’s xwOBA – expected wOBA based on angle and velocity – a bit confused. In 2017, the league-wide xwOBA – wOBA was .321 – .321, or zero. In 2016, it was .316-.318, or -0.002. This year, Statcast would expect the league to have a wOBA of .334, dwarfing the production of 2017. Instead, it’s actually .304, suggesting that MLB’s xwOBA’s had about as tough a time with projections this year as I have.

As Rob Arthur’s article argues, this pretty much screams out as a change in the ball. To be fair, there have been so many changes designed to tamp down the HR explosion in the past year or so, from Arizona’s new humidor to the league requiring balls to be kept in air-conditioned rooms, but Arthur still detects increased drag on the ball – a reversal of what we’d seen in the past few years, where drag was steadily dropping. Combine this with cold temperatures, and you’d probably expect fewer HRs, all things being equal. But the magnitude of the drop is still pretty dramatic; we haven’t seen this sharp a drop in YTY (April only) HR/9 or HR/FB in the past decade.

What’s interesting is that the drop in HRs doesn’t feel noticeable, at least to me. At a very chilly Safeco Field, I noted that the ball wasn’t carrying well at all, but then a few minutes later, Dee Gordon was rocketing a HR to right, and Mitch Haniger and Edwin Encarnacion were blasting dingers to left. At least to me, it doesn’t feel like there are fewer HRs because HRs are still every bit as important to run scoring as they were last year. Which is to say, HRs continue to be *more important to run scoring than at any time in baseball history.*

Baseball Prospectus tracks a stat called the Guillen Number, which is just the percentage of all of a team’s runs that scored on HRs. Pretty easy. For much of the past 70 years, teams scored somewhere in the range of 20-40% of their runs through dingers, and got the majority the old fashioned way: base hits, sac flies, etc. Throughout the 1950s, 60s, 70s and 80s, you’d go years and years without seeing a team crack 40%. It happened occasionally, like in 1968 when run scoring (the denominator) was so suppressed that a team or two could exceed 40%. And it happened in 1987, the culmination of a run of HRs that saw a league-wide dinger explosion that stopped *immediately* in 1988. As you got into the the expansion era, it got more commonplace, but even in the peak of the steroid era, you didn’t see teams get to 50% – the steroid era featured remarkably high run scoring overall, so the dingers were balanced by a comparable explosion in doubles and singles. Only one team got above 50% from 1950-2015, the 2010 Jays. But even as recently as 2014, only two MLB clubs topped 40%, as run scoring and dingers were both suppressed. Last year, 22 teams eclipsed 40%, with 2 above 50%.

This is the result of several trends that I and essentially every other ball writer has talked about: the increase in strikeouts, the increase in reliever innings, the potential impact of increased shifting, and the definite impact of bouncier, slicker baseballs. Unlike the steroid era, plain old base hits haven’t kept pace – they’re actually getting rarer. The steady increase in strikeouts means fewer balls in play, which is why we don’t see a collapse in BABIP. The relievers and the related-but-distinct increase in velocity help explain what we’re seeing, which leaves HRs as the big variable here. This April, league-wide BABIP is down a few points, and if history’s a guide, it’ll be in the lower .290s by the end of the year, rather than the upper .290s. Combine that with yet another increase in K rate, and you’ve got a real drag on scoring. Thus, even if HRs are down – even down substantially – from 2017, the game is still completely reliant on dingers to score. With 9-man bullpens and Shohei Otanis and Paxtons and Scherzers, it’s asking a hell of a lot to string together 3-4 hits before getting 3 outs.

So how does this impact the M’s? It’s tough to say, though again, the M’s pitchers continue to give up HRs like it’s 1999 at Coors field. One impact is that waiting for the HR tidal wave to sink the M’s wild card competitors may be a fool’s errand. The Twins and Angels haven’t been great when it comes to avoiding the HR, but they’re still more middle of the pack than Seattle. If the Angels can avoid dingers long enough for Andrew Heaney and others to get healthy, and if a drop in dingers can help Tyler Skaggs become a decent #3, that’s a problem. On the other hand, isn’t this exactly what the M’s have been counting on? They already have the fly-balling staff and solid OF defense in place; the only problem was the league HR/FB was pegged at “ludicrous.” If it’s not anymore, the M’s could benefit more than most teams. The impact on the offense is even harder to figure – the M’s have hit plenty of HRs in the past two years, so they’ve been dependent on the longball to score. But if HRs are suppressed significantly, their newfound high-average/speed approach could pay some dividends; the Royals success of 2014-15 wouldn’t have been possible in, say, 2017, but emulating the Royals in an environment that’s more 2015-y (that’s a technical term) might be feasible. It’s still early, and we’ll have to see if Safeco Field is even more of an outlier for both BABIP and HRs-allowed than in previous years, but I’m fascinated to see how this year of 4-2 games with 3 total HRs works.


One Response to “Home Runs are Down; Home Runs are More Important Than Ever”

  1. Vortex on April 13th, 2018 2:33 pm

    Very interesting. Thanks for the insights. I too am fascinated to see what transpires this year for the M’s and MLB in general.

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