The Pirates’ Road Home Run Problem

At first, it looked like pitchers that play their home games in extreme parks have extreme home run splits — that pitchers in pitchers’ parks go on the road and give up more home runs than expected. But it turns out, it might just be a Pittsburgh Pirates problem.

Staffs that leave the six most pitcher-friendly parks to go on the road have a 10.5% home run per fly ball rate, we found. But if you remove the Pirates (12%), that number for other six drops to 10.3%, very much close to the 10.1% sample average.

Take a look at the road homer per fly ball rates per team over the last five years. There’s a clear outlier.

So why do the Pirates give up so many home runs per fly ball on the road? Their division isn’t full of terrible parks — by basic park factors, their divisional opponents rank 8th, 11th, 12th, and 20th on the most hitter friendly parks. When you use home run park factors, the Reds (second) and Brewers (fifth) are homer-friendly parks for sure. But the Pirates’ average home run park factor on the road (104.5) does not explain why the team has given up 20% more homers per fly ball than the average team on the road.

One part of the problem might be ground-ball rate. Pitchers in pitchers’ parks have been going for the ground-ball at a slightly higher rate over the last five years, which might make sense because ground-ball pitchers give up more home runs per fly ball than fly ball pitchers, and those home runs could be suppressed in a pitchers’ park. But this doesn’t fly with the research Mitchel Lichtman has done about ground-ball and fly ball pitchers in different parks.

Another reason for the Pirates road problem might be the fact that the park might be changing their pitchers’ approach with respect to the strike zone. It looks like pitchers in pitchers’ parks are more aggressive and pitchers in hitters’ parks nibble more. After binning the six most pitcher-friendly by our park factors, and the six most hitter-friendly, we can look at walk and strikeout factors:

Home Park Type	Strikeout PF	Walk PF
Pitcher Friendly	101	99
Neutral	100	100
Batter Friendly	99	102

Why might this be related to the Pirates’ road homer situation? Well, we know that slugging goes up on pitches inside the zone. If a pitcher in a pitchers’ park gets used to attacking hitters inside the zone, perhaps he takes that tendency on the road and pays for it in parks that are not as friendly as his home park.

Once again, though, it doesn’t seem like our theory holds water. Check out the zone rates for the different buckets.

Home Park	Home Run Park Factor	Home Zone%	Away Zone%
Pitcher Friendly	90	48.9%	48.8%
Neutral	100	49.2%	49.0%
Hitter Friendly	112	48.8%	48.1%

We are talking about tens of thousands of pitches here, so maybe there’s the tiniest bit of a chance that the hitter-friendly pitchers are nibbling more than the other conditions. But, considering the neutral parks, there’s no evidence that pitcher’s parks pitchers are more aggressive at throwing the ball in the zone.

But it might be time to leave the pitcher-friendly teams by the wayside and focus only on the Pirates. They are in the zone 48.5% of the time at home, and 47.4% on the road. No dice there.

There are many different ways to be aggressive, though. When I asked Ryan Vogelsong about how he’s beaten his FIP so many years, he said that, basically, he’d rather give up a base hit or a home run than a walk with runners on.

Is it possible that pitchers in pitchers’ parks act differently with three-ball counts than other pitchers? Are you more likely to come deeper into the zone on a three-ball count because a ball in play doesn’t hurt you as much in a pitcher’s park?

Well, it’s not aggressiveness at home. In Pittsburgh, the Pirates walked the batter on 22.8% of the pitches they threw with three balls, against a 21.4% league average. And pitcher park staffs showed no trends.

But there is something going on in three-ball counts. Since 2010, the Pirates have given up 41 home runs at home on three-ball counts, third-least by either raw or rate stats. But on the road? They’ve given up 67 home runs, good for seventh-worst by raw stats, or sixth-worst by rate stats (per three-ball pitch).

For comparison’s sake, the Giants have given up 42 three-ball count home runs at home, and 44 on the road. The Braves have given up 40 at home, 48 on the road. The Dodgers 42 at home, 50 on the road. It’s the biggest disparity in baseball in that direction (the Blue Jays have given up 38 more home runs at home than away on three-ball counts, but that makes more sense than this).

So maybe, especially since this isn’t paired with a change in aggressiveness with respect to zone% or walk rates, maybe this is irrelevant. We know that the Pirates give up more homers on the road. Why do we care if it’s in three-ball counts or not?

Because the disparity here is larger than it is for the Pirates overall. They’ve given up 63% more home runs on the road in three-ball counts, they’ve only given up 20% more home runs per fly ball on the road in general. In fact, if you removed 20 road home runs on three-ball counts — and basically made them the Braves — you’d make the Pirates’ road home run per fly ball rate 11.4%. They’d be right next to the Mariners (road 11.2% HR/FB) instead of way out on their own.

If the Pirates gave up fewer three-ball count home runs on the road, they’d still be an extreme homer team away from home. Just less so. Sometimes, the further you drill down, the less you know or understand.