Arizona Diamondbacks Game Preview, #95: Afternoon delight?

Marcus Stroman RHP, 7-4, 5.15

Patrick Corbin LHP, 4-8, 5.25

Darwin Barney - LF	Jean Segura - 2B
Josh Donaldson - 3B	Michael Bourn - CF
Edwin Encarnacion - 1B	Paul Goldschmidt - 1B
Russell Martin - C	Jake Lamb - 3B
Troy Tulowitzki - SS	Brandon Drury - LF
Kevin Pillar - CF	Yasmany Tomas - RF
Junior Lake - RF	Tuffy Gosewisch - C
Devon Travis - 2B	Nick Ahmed - SS
Marcus Stroman - RHP	Patrick Corbin - LHP

Unlike snakes, which are most active during the heat of the day, the Diamondbacks have actually done rather better at night so far this season. Their record in night games is an almost respectable 27-34, but during the day, that sinks 13-20, which is close to 50 points less in winning percentage terms. However, they both score and allow a lot fewer runs during the day. Team runs per game conceded this year drops from 5.30 at night to 4.76 during the day, and at the plate, the same figure drops, but by less than half as much, from 4.52 to 4.30. That's unusual; across the entire NL, ERA is almost identical, day or night (4.13 vs. 4.11).

Digging a bit further into it. the main cause appears to be the defense not getting up in the morning. For there's a 26 point spike in batting average against out pitchers when the sun is out, and that appears to correlate closely to a 27 point spoke in BABIP. There is also a tendency for more balls to fly out against us during the day: one every 32.8 plate appearances these, compared to one every 34.5 PA in later games. I'd have to dig deeper to see whether this is a park effect: I know there are some parks where it is a lot harder to hit the ball out at night, but these generally seem to be ones close to the ocean - hardly the case for Chase Field!

That seems particularly doubtful because the reverse is true with our hitting. Arizona's on-base percentage is exactly the same, at .323. But the slugging percentage goes up 19 points at night, with one HR every 32.3 PA, a good deal higher than the day figure of 37.1 PA. Oddly, we also appear rather better at stealing bases during the day: our ratio there is 21-4, compared to 44-15 when it's dark. However, that's probably just small sample size, since the league as a whole does not show the same level of skew in their success rate. What does this all mean? Nothing. Except it's an afternoon game today...