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The rise and fall of the Arizona Diamondbacks offense in graphs

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Run distribution

Overall, the D-backs have scored 4.37 runs per game, almost exactly at the National League average of 4.38. But part of the issue is when they have scored them. The offense has been great at “piling on” and padding the lead - but not so impressive at doing so in close games, when one or two runs would have made the difference. As Jack noted last week, the D-backs have been particularly “good” at scoring three runs or fewer. Here’s how their scoring breaks down in percentages of games, compared to the average across the NL (AZ on the left/in red; NL on the right/in blue).

The team has been held to three or fewer runs 66 times, in 47.5% of its games so far, compared to the NL average of 45.7%. And, note, that’s the average, including the likes of the Marlins (78 such games) and Padres (75). If we compare the figure to other contending teams, the gap becomes more notable. The Braves have scored three or fewer 55 times, the Cardinals 57 and the Brewers 58. This matters, because there’s a steep drop-off in the chance of a team winning a game when they are held to fewer than four runs. Across the NL this season, here are the win percentages based on runs scored, at and around that level:

  • 0 runs, W% = .000
  • 1 runs, W% = .098
  • 2 runs, W% = .274
  • 3 runs, W% = .416
  • 4 runs, W% = .479
  • 5 runs, W% = .684

Conversely, when it comes to blowouts (games decided by five or more runs), the D-backs have a robust 24-9, record, behind only the Dodgers (25-8) in the NL. Everyone else has had at least 14 blowout losses, so Arizona is likely to win by large margins and lose by a little. As noted in a preview during the road-trip, we’re 18-25 in one-run games.

May glowers and June flowers

The contrast in production between May and June was particularly stark. In the first of those months, the D-backs scored only 77 runs, lowest in the National League this year. It made Arizona the only team to average below three runs per game for a full calendar month, at 2.85 - almost half a run worse than the next lowest (the Marlins in August, at 3.31). From May 10-23, the team scored only 23 runs over 13 games, going 1-12. But then, in just one more game the following month, Arizona brought home almost twice as many men, scoring 152 runs. That was the second-highest tally for any month by an NL club this year, trailing by one the Rockies’ total the same month (#BecauseCoors).

The chart above shows the 10-game rolling average of runs scored by the D-backs through the season to date. You can see the May slump, the June resurrection, and then it remaining fairly steady through July and August, until the slump of the road-trip through San Francisco and Los Angeles. It still hasn’t been as bad as May - we got tacos ONCE from May 1-23! - and I’m hopeful last night’s six runs are a sign of things to come. Perhaps September will turn things around for the bats, in a similar way that June did? However, Newton’s first law is likely applicable: a struggling team will tend to remain in that, unless a force acts to change the situation.

Digging deeper into the numbers

Let’s take a look into the performance of the offense, and see if we can figure out what numbers have most relevance to our offensive production. Below, are two charts. The first shows the triple-slash numbers (BA, OBP and SLG, as well as OPS) for the team this season. The second shows their strikeout rate, walk rate and isolated power (slugging percentage minus batting average) Again, these are rolling averages, based over the ten games prior to and including the date [except at the start of the year, where it may be from 1-9 games, so it’s likely to fluctuate more considerably]

You can see the general trend, and it’s not much of a surprise to see that run scoring by the D-backs is closely tied to their overall offensive numbers. But which numbers matter in particular? To get some idea, we can compare each of the six stats to the runs scored (using the rolling averages for both) to see which is the best fit. A value of 1.00 would be perfect, a value of 0 indicates no correlation. Here’s what we see, in descending order:

  1. OPS .892
  2. OBP .865
  3. SLG .834
  4. BA .798
  5. BB% .675
  6. ISO .641
  7. K% -.373

To start at the bottom, the negative figure for strikeout rate means that at strikeouts increase, scoring tends to go down. But the absolute value is quite a bit less than what we see for walk-rate. Put in non-statistical terms, walking more will help you score to a greater degree than striking out less. Power (as measured by ISO) is also a bigger factor, and you can see in the graph how this spiked during the June run. This might suggest, if you’re accepting increased strikeouts to get more home-runs, that’s probably a good trade-off. However, we haven’t quite seen this happen for the D-backs in 2018: increased K’s seem instead to lead to a decrease in power (the correlation between K% and ISO is -.280).

Walk-rate seems relatively stable compared to ISO and K%. But the road-trip slump at the end of August seems particularly to have been driven by problems getting on base. The D-backs didn’t draw a single walk over the first three games in Los Angeles; we hadn’t gone walkless in three consecutive contests since May 2014, and the time before that was back in 2009. Over a seven-game stretch, from the final contest against the Mariners at Chase, through the penultimate game in Los Angeles, Arizona had only 10 walks in 245 PA, a 4.1% rate. For comparison, Chris Owings’ career walk rate is 5.2%. So for longer than a week, the entire D-backs roster made CO look like a model of plate discipline.

The future

It’s hard to assess where the D-backs offense stands overall in relation to the rest of the National League, because they’ve played half their games in a park where the environment has changed significantly from last year. Some park-adjusted metrics like wRC+ OPS+ may be inaccurate, if they use multiple years of data - so right now, a chunk of the park factor for Chase is based on pre-humidor numbers. This probably makes the offense look worse than it “actually” is. But even taking park factor away entirely the team ranks 12th for BA, 11th for OBP and 10th for SLG, They’ve actually scored more than you’d expect from that, their 607 runs being 9th in the league. Good base-running and RISP performance has helped.

It is possible to reach the post-season averaging 4.37 runs per game, but it isn’t standard. Of the 60 teams in the two-wild card era (2012-17), nineteen have done so with a lower rate of scoring, but none did so last season. The lowest rate then was the Dodgers’ 4.75 runs per game, though the MLB run environment is down this season. It’s closer to what it was in 2016, when the Mets reached the playoffs despite scoring only 4.14 R/G. The problem for Arizona is that even their 4.37 average is skewed by June. Over the last thirty games, since the start of August, that figure is more than half a run lower, at 3.83. To have a chance, we need more than that down the stretch, and given the schedule, it won’t be easy.