What’s Wrong With Goldy at Home?

One of the big narratives this season is why is Paul Goldschmidt so great on the road yet so not-Goldy at home? For his career, Goldy is a 148 wRC+ on the road and a 142 wRC+ at home - pretty close. However, for 2018?

Home: 108 wRC+

Away: 193 wRC+

This is just bizarre. First of all, that road 193 wRC+ is borderline legendary - tied for 4th-best since 2000 behind Barry Bonds (twice) and Mike Trout (2018). But that home wRC+ just seems bizarre. Since 2013, this has been Goldy at home:

2013: 153 wRC+

2014: 158 wRC+

2015: 174 wRC+

2016: 135 wRC+

2017: 165 wRC+

2018: 108 wRC+

It just doesn’t make sense, especially given his surge on the road. What gives?

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And we’ll cut straight to the chase: exit velocities.

A pretty standard split from 2015-2017, given Arizona’s extremely hitter-friendly ballpark before a complete reversal in 2018. On one hand, what Goldy is doing on the road this season is truly remarkable. But the sudden drop at home is just bizarre. Flyballs aren’t any better:

The graph does change a bit here, as Goldy had a better away FB exit velo in 2015, his best overall offensive season. Is that telling for this season?

The easy answer here is to blame the Humidor. However, its effects are still largely unknown and many players on the Dbacks have improved at home despite the Humidor. Also, it appears that this is deeper than that, at least with regards to Goldy.

Could there be something with Goldy’s approach? Or at least how he’s being pitched to? The data suggests that this might very well be the case.

Let’s take a look at how Goldy is being pitched. These next two charts are going to be the percentage of pitches thrown in the strikezone for Goldy and the percentage of pitches in the strikezone that Goldy has swung at. The shape of these charts are what’s important:

There are two important things to notice here. First is that the overall shape of these is similar, meaning the way Goldy swings at pitches in the strike zone hasn’t overly changed (the way Statcast handles this is that the Sw% chart is Goldy’s overall swing rate for total number of pitches, not just pitches in the strike zone).

The second, and bigger takeaway, is that Goldy is not seeing strikes at home. By a fairly substantial margin. This will ajdust a bit as the Dbacks have played more road games than home games, but that won’t account for nearly this entire gap. Also notice: this is the same thing that happened in 2015.

So one of the things that has been going against Goldy at home this season is that he just isn’t getting strikes to hit. That’s probably the prime driver as to why his home BB% is 16.5% and his road BB% is only 11.3%. The inverse of this chart also explains why Goldy is doing so well on the road: give him strikes to hit and he’s going to destroy you.

However, Goldy is not infallible here, as his approach is struggling. His home ISO is .155 and his K% is at 27.0%. With a home wRC+ of 108, there has to be more at play here:

Goldy has been taking his walks but sure enough, he’s chasing at a rate that isn’t Goldy like. This is likely very much a mental thing as Goldy probably wants to put a ball into play on occasion. Speaking of putting balls into play...

Goldy is really struggling to put balls into play at home. This appears to mostly be a combination of strikeouts, walks, and foul balls at play here. But it appears to play into the mental aspect above (or vice versa). The lack of strikes probably isn’t the only driver of Goldy’s struggles at home but it appears that a large element of it might be a mental factor.

It’s convenient to blame the Humidor but it’s way too early to make any meaningful conclusions on its effects, especially on an individual batter level. And maybe the Humidor has had a part in Goldy’s mental approach. Whatever it may be, there is more at play to Goldy’s struggles than just the Humidor.