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Putting Dan Straily’s Theory to the test

Does playing in a hitter-friendly park make batters more prone to chase?

Miami Marlins v Philadelphia Phillies Photo by Mitchell Leff/Getty Images

Before his start on Wednesday, Dan Straily had a locker room interview with Jessica Blaylock, where he was asked a set of rudimentary questions about how he felt going into his start against the Philadelphia Phillies. Although the interview was pretty routine, Straily said something that made me scratch my head, do some research, and then write this article.

When asked about how he felt having to pitch in Citizens Bank Park, Straily said he was excited to do so. Citizens Bank Park, the home of the Phillies, is a notorious bam-box. Ranking eighth in park factor, when I think of Citizens Bank Park, I can think of many a home run hit. Basic intuition tells us that in a ballpark as hitter-friendly as Citizens Bank, a pitcher should be less than eager to take the mound. Needless to say, I was initially confounded.

Nevertheless, Straily justified his assertion by explaining that in a ballpark like Citizens Bank, pitchers can get the edge by making batters chase pitching outside of the zone. In so many words, Straily proffered that while a batter in an unfriendly ballpark is more apprehensive at the dish, when a hitter steps into the box at Citizens Bank Park, his eyes get wide as he knows the park has a reputation for letting the ball fly. As a result, a batter may be more prone to chase pitches off of the plate in bouts of over-aggression.

It’s a definitely a head-scratcher, but it doesn’t not make sense. Here’s a story.

In Broward County from 2005 to 2008, slow pitch softball for middle school boys was offered as an interscholastic sport. As a lifelong baseball player, I tried out for the Glades Middle softball team, and made the squad in seventh grade. One day, we had a game against a rival middle school, Falcon Cove. After school, we boarded the bus and arrived at Falcon Cove’s feeder high school, Cypress Bay, where we would play on the Cypress Bay women’s softball team’s field. As the bus pulled up, everyone on the bus got wide-eyed as we discovered the dimensions of the field — 200-foot fences.

Seldom the pre-pubescent teenager has the body strength to hit the ball 300-plus feet over the fence at most baseball fields. However, given the size of the softball field, this was as good a chance as ever for all of us to take our first home run trots.

Still, my expectations weren’t very high. Having been of smaller statute my entire life, I doubted my chances of powering one over the fence. I planned on coming out and focusing on hitting line drives, just as I always did. As the lineup progressed, I watched almost all of our batters step up to the dish and take over-aggressive, mammoth hacks in an attempt to knock a dinger. Many popped up to the outfield or topped dribblers to the infield.

Then I stepped up to the dish; as I watched the big yellow softball tumble in through the zone, I threw my hands at the ball — although I got under it for the most part, the ball snuck over the left field fence. That was my first and last over-the-wall home run.

This story isn’t just to tell you about my first home run. That’s just an extra gift. The moral of the story is that there may be something to Dan Straily’s theory. Although the plate discipline of middle school softball players can hardly be compared to that of Major League Baseball players, the story speaks to our carnal, most basic and essential human desires to hit dingers. Theoretically, if the opportunity is there, then baseball players are going to go for it. And if baseball players are going to go for it, Straily is going to take advantage of it.

To see if Straily was onto something, I looked into park factors and plate discipline statistics. Park factors are computed values used to adjust different statistics. In the realm of sabermetrics, almost any time there is a “+” or “-” next to a statistic, such as in wRC+ or ERA-, it means that the statistic has been park adjusted in the interest of comparing it to league average. The park factor is somehow calculated into the specific stat in order to adjust said stat in light of any advantages or disadvantages the environment may yield.

Park factors in general are calculated by taking a team’s production at home, dividing it by a team’s production on the road, and then multiplying it by 100. The resultant number represents at 162-game total of the percentage of production a team earns/loses by playing in its home park. Because teams only play 81 games in their home ballpark, the amount above/below 100 is thus multiplied by two in order to get your final statistic.

In practice, according to, the park factor for Marlins Park is .856. Although it’s common practice to do so, ESPN doesn’t multiply their home production divided-by road production total by 100 — for the rest of this article, we will use ESPN’s numbers and multiply it by 100 ourselves. This brings Marlins Park’s park factor to 85.6. When we subtract 85.6 from the average 100, and divide it by two, we derive that the Marlins are experiencing a 7.2 percent deficit in run production by playing at home this year. While ESPN displays park factors for this season only, many other popular websites such as Fangraphs and Baseball-Reference regress their park factors to multi-year totals.

Here are some numbers.

Park-by-park plate discipline

Ballpark Home Team Park Factor Park Factor for Home Runs Park Factor for Doubles Home Team Swing % Home Team Swing % Rank Home Team O-Swing % Home Team O-Swing % Rank
Ballpark Home Team Park Factor Park Factor for Home Runs Park Factor for Doubles Home Team Swing % Home Team Swing % Rank Home Team O-Swing % Home Team O-Swing % Rank
Coors Field Rockies 130.6 121.1 117 47.2 8th 30.6 12th
Target Field Twins 112.4 115.7 111.8 44.4 28th 26.8 28th
Citizens Bank Park Phillies 108.2 141.2 98.5 47.1 10th 30.9 11th
Yankee Stadium Yankees 102.9 130.6 81.9 45.5 22nd 28.5 24th
Oriole Park at Camden Yards Orioles 102.6 129 87.8 48.1 5th 33 3rd
PNC Park Pirates 94.8 86.5 108.2 45.8 19th 28.3 27th
Kauffman Stadium Royals 93.5 81.1 114.7 50.6 1st 33.6 2nd
AT&T Park Giants 85.9 62.8 100.1 47.5 6th 29.1 18th
Marlins Park Marlins 85.6 81.6 74.8 46.5 13th 31 8th
Petco Park Padres 82.1 72.7 89.4 47.3 7th 31 9th
O-Swing % — Outside-the-Zone swing percentage Park Factors courtesy of | Swing discipline data courtesy of

From the list of park factors on, I initially selected the first five ballparks with the highest park factors and higher park factors for home runs than doubles. This emulates the thrust of Straily’s argument; when he was talking about over-excited hitters, he was inferably talking about hitters over-excited about hitting homers, not doubles. For the other end of the spectrum, I also added the five ballparks with the lowest park factors and lower park factors for home runs than doubles.

It’s worth mentioning that I’m leaving 20 other ballparks/teams out of the equation in our exercise. While in other exercises this might create sample issues, I believe it’s okay to omit these items here. We’re talking about ballpark reputation here. So the further you get closer to the average ballpark, the lower the effect of reputation gets. We don’t really care about ballparks with no reputation. We want to know how teams swing when they step in the box at mile-high Coors versus how they swing playing in muggy San Diego.

When looking at the graphs, you should hone in on the 100 park factor meridian; a 100 park factor ballpark is one with about average conditions. Hypothetically, if Straily’s theory holds water, then the dots on the right side of the 100 mark should be higher than the dots on the left side of 100.

The data on just swing percentage seems to lack any perceptible trend. From what I gathered in my freshman-year statistics class, in order to derive a correlation between the variables, you draw a line of best fit. For the graphs based on just swing percentage, I would submit that it’s almost impossible to find any correlation whatsoever.

But we’re more concerned here about outside of the zone swings — that’s what Straily focused on. By making feisty hitters go outside of the zone for quality pitches, a pitcher could in theory defeat an order. From the ten ballparks, the data on swings outside of the zone is more concentrated, so a line of best fit could be drawn here. However, instead of evincing a positive correlation — as we hypothesized it would — the lines of best fit would probably have negative slopes.

You can thank the Royals and the Yankees for that. As you can see from the table and the graphs, Kauffman Stadium is particularly unfriendly to hitters. However, although the Royals’ production suffers a 3.25 percent deficit at home, and their home run production takes a 9.45 percent hit, percentage-wise the Royals still take more outside-the-zone swings than 28 other teams.

On the other hand, in the launchpad they call Yankee Stadium, where the Yankees get a 1.45 percent boost in total production and a 15.3 percent boost in home run production, the Bronx Bombers still manage their discipline, ranking 24th in outside-the-zone swing percentage. These outliers directly contrast Straily’s theory.

So it doesn’t appear that Straily’s theory checks out. Ultimately, the theory ignores many important other factors that come into play. It’s the product of a very old-school intuition that just can’t survive the amount of statistics and technology that batters have at their disposals to construct their approaches. It also ignores the fact that batting coaches exist, and probably regardless of the stadium, players are instructed to take certain approaches against certain pitchers.

As we mentioned earlier in the article, you can synthesize a theoretical construct where Straily’s strategy makes sense. However, in the end, there is an amalgam of stats that refute the theory, and these very stats can be used to turn the tables. Also, science words are cool.

Still, Straily appears to have a game plan. Among all qualified starters, Straily ranks tenth in the league in O-Swing percentage and 29th in soft contact created. His game is forcing uncomfortable contact, and when he steps to the rubber, he has intent to execute that plan.

So let’s look at the finished product. Who would win in a fight, park factors or plate discipline?

The Phillies got to Straily for eight earned runs, including home runs by Rhys Hoskins and Odubel Herrera. Listen to :20 when he starts talking about his approach against Hoskins and Herrera. The game plan was there. The question is whether he executed.

The pitch was indeed high-and-in, so he did execute. But it’s Rhys Hoskins, and the dude is on fire right now, so you can’t blame Straily for this one. Forget that this one probably would have left any park, park factors win round one.

On the other hand, you can chalk this one up to plate discipline. Straily either missed or was trying to sneak one across. Herrera took advantage of it.

With the exception of the Hoskins home run, on the scoring plays, the Phillies took advantage of pitches that caught a lot of the zone. One more stat not mentioned above that was probably circulating in Phillies locker room pre-game: Straily ranks 28th in pitches thrown in the zone with 46.1 percent. About half of his pitches find the zone. If you take one more step and pull up his heatmaps, you see that when Straily leaves it in the zone, he leaves it right where batters want it.

Straily’s pitchmap for the season v. Wed 9/13 vs. PHI and

That’s the book on Straily, and last night, the Phillies had it read cover-to-cover. Dan Straily is one of the more cerebral pitchers in the game. As a notorious disciple of Driveline, Straily is probably more sabermetrically-oriented than your average pitchers. Thus the reason for his statistics-driven game plan. However, given the numbers, it’s not unbelievable to think that if a batter can lay off the junk and make Straily come to him, he can get a pitch to drive.

I think the bottom line is that no matter where a pitcher plays — Petco or Coors — or who he faces, location will always rue the day for him if he can’t reign it in. As we can see, it doesn’t matter what a pitcher tries to do with a pitch, but what he actually does with it and where it ends up. A long popular theory is that the best pitchers establish dominance on the inside half of the plate. Whether that is true or not can probably be explored in another article. But what we know for certain is that if you are an MLB pitcher, and you come inside and miss — as Straily did with Odubel Herrera and other Phillies on Wednesday — you’re going to pay the price.

And as we have found out in today’s science experiment, it’s here that park factors come into play. Contrary to Straily’s belief, we’ve proven that it probably wasn’t the hitter-friendly environment of Citizens Bank Park that made Odubel go after the first pitch in his at-bat. It was probably the center-cut location of the pitch. After Herrera puts lumber to rawhide, park factors then come into play. While the ball flies out of cozy Citizens Bank Park on a clear night, it’s less certain that the ball punctures a hole in Petco’s Marine Layer and does the same.

This article by no means is any attempt to add insult to the injury of Straily’s last start. As the Marlins’ return in a trade that saw highly touted prospect Luis Castillo head to Cincinnati, Straily brings an unappreciated amount of pressure with him to the mound every start. Straily has shown many bright spots this season, and by all means, he isn’t having a terrible season (2.0 fWAR, 100 ERA-, 107 FIP-). But while you have to give him credit for going out to the mound with a plan every fifth night, we now at least have evidence that he might need to change his game up if he wants to find success in hitter advantageous ballparks in the future.

2017 park factors from ESPN

Statistics courtesy of

Information on park factors from Fangraphs and Wikipedia