Let’s look at the Diamondbacks’ batters this season through 16 May. Their innings differed in some interesting ways.
How well the batters hit was represented wOBA which measured how much their plate appearances impacted their projected runs scored.
The worst inning was the fifth inning. But before we look at the reasons, let’s look at the best innings.
Their best innings were the second, third, and seventh. Although it may be nearly impossible to determine all the contributing factors, a few may be significant.
- In the seventh inning, it appears that they exercised excellent plate discipline to walk more often and strike out less often. Simple explanations are sometimes most insightful.
- In the second and third innings, the Diamondbacks hit home runs more frequently (HR/PA). The second inning is by far the most interesting.
Before looking deeper at their innings, the following table shows some statistics for each inning (excluding the one game with extra innings).
Did lower swing frequency impact the second inning?
An important caveat is that although the batter ultimately decides how frequently he swings at pitches, his starting point is the pitches that pass in front of him. Pitchers can vary whether those pitches are hittable and whether those pitches are in or near the strike zone. Another important factor is whether the pitcher adjusts his pitches based on how often the batter swings.
In the second inning they lowered their swings per pitch, which seemed to lower their BABIP and raise their home runs. Although this may be statistical coincidence, runner(s) on base may have triggered the batters to lower their swing rate and thereby hit more home runs. In all innings except the second inning, 42% of home runs happened with runner(s) on base. In the second inning 60% of the home runs happened with runner(s) on base. On the other hand, if we exclude Geraldo Perdomo’s 3 homers in the second inning, only 43% of home runs happened with runner(s) on base.
Home runs are worth more than hits. This season for the Diamondbacks, the average non-homer hit was 1.275 bases for the batter (average of singles, double, and triples), while home runs were worth 4 bases for the batter. For the second inning, the low BABIP (.302) over 138 balls-in-play may be less important than the high HR/PA (.049) over 183 PAs. My intuition is that in the second inning that tradeoff helped score more runs.
What impacted the fifth inning?
The fifth inning had a much lower wOBA (.277) than any of the other nine innings. The following did NOT cause the lower wOBA.
- Did Diamondbacks batters suffer from bad matchups when relief pitchers entered the game? No. In the fifth inning when Diamondback balls-in-play resulted in outs, only 32.5% were from a relief pitcher (the starter was still in the game for 67.5% of those outs).
- Did the Diamondbacks try too hard to hit either grounders or fly balls? No. They were balanced with 16 fly outs and 17 ground outs.
The surprising reason was that the Diamondbacks had many PAs with two types of batters in the fifth inning. The two types follow:
- 34 PAs by batters having a career best (or second best) batting season (all innings). Those batters were Lourdes Gurriel Jr. with a 152 OPS+, Pavin Smith with a 112 OPS+, and Christian Walker with a 135 OPS+ (second best season for Walker).
- 28 PAs by batters who have since been optioned to the minors. Those batters were Alek Thomas with a 59 OPS+ and Jake McCarthy with a 30 OPS+.
The good news is that going forward the wOBA will improve immediately, and when the batters return to the Majors, they will likely have improved their batting.
Did swing frequency impact wOBA?
This season for the Diamondbacks other factors seemed to be more important influencers of wOBA. A scatterplot of innings (not shown) did not indicate a significant correlation.
Did swing frequency impact BABIP and Walks?
With the important caveat that there may not be a significant impact on wOBA, this season for the Diamondbacks it appears that swing frequency may have impacted BABIP and walks.
The following table shows the relationship between swing frequency and BABIP
The following table show the relationship between swing frequency and walks.
The best innings were the second, third and seventh, while the worst inning was the fifth.
In the second inning Diamondbacks batters lowered their swing frequency and hit more frequent home runs. They had excellent plate discipline in the seventh.
In the fifth inning, two types of batters predominated - batters with career best OPS+ and batters who have since been optioned to the minors. The batting results in the fifth inning should improve, both immediately and long term.