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The humidor at Chase Field: 30 games in

No truth to the rumor a repair crew was seen arriving at Chase Field late last night...

Heating Radiator And Thermostat Photo by Sean Gallup/Getty Images

Last night, the Diamondbacks tied a franchise record, clubbing six home-runs in a 9-1 victory over the Marlins. It was just the latest in an offensive barrage, which has seen the team score 30 runs over the first four games of the homestand. Combine that with dismal offensive production during the nine-game road-trip, in which Arizona scored an average of only two per contest - with half of the production coming in a single game - and it would appear the effect of the humidor has been dampened of late. But let’s see what the numbers say.

Runs scored and allowed

As this is purely based on performance Chase, the road-trip doesn’t have an impact here. And since it includes both the Diamondbacks and their opponents, things haven’t perhaps changed as much as you’d think. Last year, there were a total of 803 runs scored in Chase, an average of 9.91 runs per game. So last night’s shellacking won’t have moved the needle all that much: while the Arizona offense was on fire, the Miami one was all but shut down by Clay Buchholz, and so the total runs scored was only fractionally above last year’s average, at 10. We may have scored 30 runs in four games, but having only conceded 15, the total of 45 is barely a handful over the expected rate last season.

So far, only four games of the thirty this year at Chase have seen more than eleven runs scored in total. Curiously, the D-backs have won them all: 9-8 over Colorado in the second game; the 15-inning 8-7 victory over the Dodgers; 8-5 over the same opponent on April 30; and the 12-5 pounding of the Reds which opened this home-stand. I’ve added a third line to the chart below, showing the difference in total runs between 2017 and 2018, and you can see that has largely flat-line of late. The current difference (+84) is almost unchanged from what it was after the 22nd game at Chase (+82).

Overall offense

However, even if only keeping pace with 2017 scoring, this still represents a rebound from the historically low levels we saw through the first twenty games. At that point, the overall ERA at Chase was 3.20, 28th in the majors and a run and a half down on the 2017 figure. Ten games further on, this has ticked up to an ERA of 3.50, four places further up the list. The ball has certainly been flying out of Chase better: helped by last night’s long-ball barrage, 29 home-runs were hit in the last ten contests in Phoenix, compared to 35 over the first twenty. The overall tally is 64, which puts it 14th - it’s actually one more home-run than has been hit at Coors Field to this point! [Albeit in five more games]

All these bombs won’t have had an impact on BABIP, and that hasn’t changed very much since we last checked in. The Chase figure is up two points to .270, which remains ahead only of Nationals Park in Washington. But the home-runs do count towards batting average at Chase, which is no longer dead-last, having gone up to .223, good enough (or, not bad enough, I guess!) for 28th. Curiously, the “fun-sized” park in Houston is one of those below us. It’s playing very similarly to Chase across these categories, with a .221 average and 63 home-runs there, along with a .275 BABIP.

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 30 games at home and 26 on the road:

  • Home: .221/.301/.380 = .681 OPS
  • Away: .212/.283/.380 = .663 OPS

This is a radical change, almost entirely the result of the road offense cratering. After 20 games, our OPS away from Chase was .737. But a nine-game road-trip where the team batted a collective .168/.231/.276, a .507 OPS, has dragged the season figure away from home down by 74 points. In contrast, the home figure has remained almost unchanged, ticking up by three points. Good though the bats have been on this home-stand, it has so far only been able to negate the awful hitting the Diamondbacks delivered at home against the Nationals and Brewers just before the road-trip from hell. Those six games saw a .167 average and .484 OPS. We’ll need a few more performances like last night.

But it was still enough for normal service - at least relatively speaking - to have been resumed. The 2018 Diamondbacks have now joined all twenty of their predecessors, and are currently hitting better at Chase than elsewhere. The margin is still only 18 points, and it’s definitely worth noting that we still have yet to play in Coors, whose OPS of .814 is highest in the majors. That will have been addressed with three in Colorado by the next time we check in, after the penultimate game of the month against the Giants on June 29.