San Francisco’s Secret Home-Field Advantage

ATTPark4
ATT Park, from behind home plate, at game time for a night game.

Justin Upton has hit the ground running in San Diego. His power stats have not suffered as much as you might expect, at least, as his isolated slugging (.194) and home runs per fly ball (16.7%) are right in line with career norms (.201 and 15.1%, respectively). When I asked him about hitting in San Diego, he shrugged it off. He also said something interesting about San Francisco’s park.

“The one thing I look for in a park is whether you see the ball well and Petco Park is a great place to see the ball,” Upton told me. “There are certain places where there are bright backgrounds or things like that. I’m all about seeing the ball, then I can square it up. More during day games. Most parks have done a great job of making sure the backdrops are good. But in some day games, in certain areas of the park, like in San Francisco, there’s the stands on both sides, where it can get a little bit bright.”

This sort of thing is tough to test. But let’s say that AT&T park was bright during the day. Presumably that would change the offensive numbers during the day, and since the home team might be more used to it, it would affect the away team’s numbers more.

Below is a table that shows a comparison of day-game scoring to night-game scoring since AT&T Park opened in 2000. We’re looking at scoring through eight innings, since the ninth inning offers problems of its own. What we’ve done here is divide day scoring by night scoring for both the home and away teams. Then we’ve subtracted the difference between home and away to get a crude home-field advantage with respect to day-game scoring divided by night-game scoring.

What you’ll see is that the Giants have scored more in day games than night games, but their opponents have scored about the same in day and night games. Given that temperature is a big component of offense, this alone gives a whiff of truth to what Upton is saying. But, if you sort this for the league, you’ll see that other parks have bigger day/night discrepancies.

Team Home Day% Away Day% Home-Away
Mets 104.0% 92.0% 12.1%
Astros 110.8% 99.0% 11.8%
Tigers 102.0% 90.9% 11.1%
Braves 112.8% 102.0% 10.8%
Angels 99.0% 88.2% 10.8%
Nationals 101.6% 91.3% 10.4%
Red Sox 102.9% 94.3% 8.6%
White Sox 100.4% 92.0% 8.4%
Cardinals 99.4% 94.2% 5.3%
Reds 100.6% 95.4% 5.2%
Padres 110.8% 106.1% 4.7%
Cubs 106.4% 102.2% 4.2%
Royals 104.7% 100.6% 4.1%
Yankees 106.9% 102.8% 4.1%
Blue Jays 94.5% 90.7% 3.9%
Giants 102.9% 100.0% 2.9%
Dodgers 98.9% 97.5% 1.3%
Mariners 99.8% 98.5% 1.3%
Marlins 100.8% 99.5% 1.3%
Phillies 106.7% 107.5% -0.8%
Rangers 89.0% 90.2% -1.2%
Athletics 99.5% 102.7% -3.2%
Rays 90.8% 94.0% -3.2%
Rockies 97.7% 100.9% -3.3%
Twins 95.8% 100.0% -4.2%
Indians 93.5% 97.7% -4.2%
Pirates 93.8% 99.5% -5.7%
D-backs 88.2% 94.4% -6.2%
Brewers 91.5% 108.0% -16.5%
Orioles 88.1% 109.3% -21.2%

I asked Will Venable about the park as well, and he agreed with Upton and pointed out that this extends into night games as well.

“During batting practice, it’s really bright,” said Venable. “Those empty bleachers are so bright, and the sun is setting behind you, so the light is pointing right at those seats. It can happen some in the first inning, too. I’m glad when I’m not leading off here. These parks are so great and professional, it’s not that big a deal, but you do notice when something is only a tiny bit off.”

ATTPark3
ATT Park minutes before visitor’s batting practice.

So now we switch it over to night games. What this table shows is the average first-inning score divided by the average (cumulative) eighth-inning score for the home and away teams. How much scoring is done in the first inning by the home and away squads in each park? Then we subtract the away from the home to find a “first-inning home-field advantage.” Look who’s first.

Team Home Score% Away Score% Home-Away
Giants 16.50% 12.88% 3.615%
Brewers 16.03% 12.55% 3.488%
Angels 13.16% 10.15% 3.015%
Blue Jays 13.19% 10.69% 2.503%
Cardinals 14.98% 12.54% 2.444%
Braves 14.64% 12.38% 2.257%
Yankees 14.80% 12.67% 2.136%
D-backs 14.97% 12.99% 1.974%
Red Sox 13.73% 12.14% 1.591%
Marlins 15.68% 14.15% 1.531%
Indians 13.72% 12.22% 1.509%
White Sox 13.74% 12.26% 1.471%
Phillies 15.35% 14.10% 1.243%
Reds 14.80% 13.56% 1.240%
Royals 14.22% 13.08% 1.144%
Rangers 12.25% 11.63% 0.624%
Padres 14.48% 13.96% 0.524%
Orioles 12.94% 12.43% 0.509%
Twins 13.06% 12.82% 0.236%
Cubs 13.50% 13.29% 0.207%
Dodgers 15.59% 15.41% 0.181%
Pirates 14.89% 15.20% -0.315%
Athletics 12.65% 13.04% -0.390%
Mariners 12.85% 13.26% -0.410%
Nationals 14.09% 14.59% -0.497%
Astros 14.57% 15.33% -0.763%
Rockies 13.57% 14.42% -0.850%
Mets 13.67% 14.79% -1.112%
Tigers 12.61% 14.11% -1.492%
Rays 11.44% 13.63% -2.188%

So the Giants have the largest first-inning home-field advantage in baseball. They score many of their runs in the first inning — maybe because it’s warmer — while their opponents score a much smaller percentage of their runs in the first inning. Maybe because the center-field bleachers are bright.

One of the amazing things about baseball is how different each home park is. That also makes it hard to analyze home-field advantage, since the temperature, humidity, and wind patterns change from game to game, from year to year… and from inning to inning. The Giants probably didn’t plan to have this home-field advantage through their batting eye, and it may not amount to much in the grand scheme of things, but it’s still remarkable that they enjoy any advantage because of the materials used in building their center-field bleacher seats.

We hoped you liked reading San Francisco’s Secret Home-Field Advantage by Eno Sarris!

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With a phone full of pictures of pitchers' fingers, strange beers, and his two toddler sons, Eno Sarris can be found at the ballpark or a brewery most days. Read him here, writing about the A's or Giants at The Athletic, or about beer at October. Follow him on Twitter @enosarris if you can handle the sandwiches and inanity.

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Avattoir
Guest
Avattoir

It’s possible this otherwise excellently conceived article would be if anything even more compelling if the Giants actually had a winning record at home this season.

McNulty
Guest
McNulty

He says the advantage lasts only for the beginning of the game….

channelclemente
Guest
channelclemente

It’s also horse hooey.

dodger fan
Guest
dodger fan

My antenna instantly perked up because it could represent part of the reason the dodgers win so little against a team that can barely remain at .500.

dodger fan
Guest
dodger fan

at home, sorry