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The humidor at Chase Field: 40 games in

Things appear to have stabilized somewhat at Chase Field - at least in the macro view

Heating Radiator And Thermostat Photo by Sean Gallup/Getty Images

The number of home games continues to increase, and we now sit at about the half-way point of the first season with the humidor at Chase Field: 40 games have been played and there are 41 to go. As our sample size increases, you would expect the wide variations to settle down a bit, as the randomness which is inherent in a single game of baseball and its scoreline, continues to be diluted. That does appear to be the case, at least in some aspects.

Runs scored and allowed

We had all manner of contests at Chase in the last 10 games, which takes us back to the second game of the series against the Marlins. The D-backs went 6-4 overall, but the manner in which those games were decided covered all the bases from blowouts to squeakers. There were pitching duels, like last night’s 2-1 loss to the Giants, and we saw five occasions where a team was held to two runs or fewer. But the D-backs also delivered tacos to their fans six times, and if the same applied to the opposition, they wouldn’t have gone hungry, scoring 5+ runs on five occasions. This peaked in the 13-8 slugfest over the Pirates, on June 12: the 21 runs was most in a game at Chase this year.

This and the 9-5 win the previous night against the same opponent continued the trend noted last time. Arizona are now 6-0 in games at Chase where more than eleven runs are scored. Those games also helped keep the difference in runs between this season and last in check. After 30 games, the total was down by 84 compared to the first 30 games in Phoenix of the 2017 season. Ten more contests in, and the difference has barely changed, now sitting at -88. [And before yesterday’s 2-1 game, it had actually narrowed, and was sitting at -80] Has the humidor been adjusted? Or is it players that are changing their approach?

It may be significant that a decline in the D-backs offense is responsible for most of the gap. At this point last year, Arizona had outscored its opponents by a margin of 251-154. Both figures have dropped in 2018, but it’s now 174-143: runs scored are 77 lower, runs allowed only 11 down. Of course, there may well be other factors contributing to this, such as differences in personnel for Arizona this year, as well as the overall decline in MLB offense. [Going into last night, runs per team per game were down 0.28 across all of baseball, which basically matches the drop we see in visitor offense at Chase in 2018]

Overall offense

With a total of 35 men crossing home-plate in two nights against Pittsburgh, the ERA at Chase this year took an unsurprising and significant jump upwards. It climbed by more than half a run over the last ten games, going from 3.20 to 3.73. While still significantly lower than both MLB average (4.06) and the 2017 figure (4.70), the gap is at least now in reasonable territory. The steady increase we’ve seen is bucking the overall trend across baseball. It’s usually said that as the weather heats up, so do offenses, but on the last day of June, the ERA across all baseball is the lowest for a month this year. It was 4.12 in April, but declined to 4.05 in May and 4.02 this month.

That ERA ranks Chase Field 22nd across the thirty main ballparks, again considerably lower than the seventh spot from last season. Colorado is still top, even with their humidor, Coors Field having an ERA of 5.55 so far. Two thoughts. I wonder what it’d be like without the humidor? And let’s not forget, the Rockies shelled out nine figures this winter on bullpen arms, and are still “enjoying” the highest relief ERA in baseball. Don’t worry, Dinger - only two and a half more seasons on those contracts. 22 HR hit at Chase over the last ten games, about the average this year. We’re now at 86, and on pace for a drop of about forty or so, from the 215 hit in the regular season there for 2017.

Home/road splits

A quick refresher. Over the first twenty years of the franchise, the team has always hit better at Chase Field than elsewhere. The amount has varied, from a mere three OPS points in 1999, to 136 points last year, but it has been a consistent feature for two decades. Of course, run environments have shifted dramatically in that time, as we went through the steroid era and came out the other side. But it’s the difference which we’re interested in, and from 1998 through 2017, here’s the sum total of the Diamondbacks home/road offense:

  • Home: .269/.338/.442 = .781 OPS
  • Away: .248/.315/.394 = .709 OPS

Now, let’s look at those same figures for the Diamondbacks’ performance at the plate in the 2018 season. We’ve played 40 games at home and 42 on the road:

  • Home: .228/.311/.391 = .702 OPS
  • Road: .225/.298/.399 = .698 OPS

We are still seeing an edge in favor of Chase Field, but it’s now the slimmest of them: 18 points last time, it has now dropped to just four. You can see the road offense is down a tick - perhaps tied to the overall decrease across baseball mentioned above. It might be worth noting we still have yet to play any games in Petco. On the other hand, the ERA there is half a run higer than at Chase, so it may not be quite the difference maker you would expect! Our hitters have hit nine more homers on the road, 51-42, while Arizona’s pitchers have allowed two more, 46-44. But it is affecting some more than others? Here are our regular hitters, ranked by home OPS - road OPD (+ve = better at Chase).

  1. Descalso: +341
  2. Dyson: +119
  3. Marte: +92
  4. Pollock: +91
  5. Murphy: +68
  6. Peralta: +30
  7. Owings: +23
  8. Ahmed: -85
  9. Lamb: -148
  10. Goldschmidt: -394
    (min 60 PA each home and away)

Quite a startling difference. Perhaps this is why Daniel Descalso is so beloved of fans, because he has been hitting like Goldschmidt in from of them at Chase Field. Except, of course, Goldschmidt hasn’t been hitting like Goldschmidt there!