The Bigger Picture - The Miseducation of Park Factors

May 21, 2021

Pierre Camus examines park factors early in the 2021 MLB season and the fantasy baseball impact.

Another no-hitter in the books. Something's in the water or, more accurately, in the baseballs. We already covered that topic last time so let's figure out how to extract more offense from our daily or weekly lineups.

Home/road splits seem like a good place to start and we know certain stadiums play friendlier to offense than others. A batter in Coors Field is a sure bet. Dodger Stadium is a notorious pitcher's park, so prioritizing pitching over hitting seems logical, especially in DFS where we're looking for HR potential. But what if I told you that L.A. has ranked above league-average in Park Factor for home runs five years in a row? Or that two stadiums that ranked among the highest in HR Park Factor in 2019, our last full season, are both bottom-10 this year?

You could say some parks just "hit different" these days. But that's not it at all. Taking a cursory glance at Park Factors can lead to serious miseducation if we don't recognize the underlying causes for yearly variance. Let's break it down and figure out what factors go into park factors and which we can trust.

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Ex-Factor

For those unfamiliar, here is the definition taken from MLB.com:

Ballpark factor, at its most basic, takes the runs scored by Team X (and its competitors) in Team X's home ballpark and divides the figure by the runs scored by Team X and its competitors in Team X's road contests.

A bit further down, "It isn't affected by the teams or players involved, because those teams and players are also playing games in other stadiums."

OK, so apples to apples, right? That means parks should be fairly steady in terms of performance from year to year, assuming nothing has changed structurally like fences being moved in, retractable roofs being built, etc.

In that case, let's see if it holds true over the past five full seasons (we'll throw in 2020 just for kicks this time).

To simplify things, I'll exclude Toronto, Buffalo, Dunedin, and any temporary parks that shouldn't be factored into lineup decisions. It's pretty basic anyway; if a hot offense is playing at a minor-league park, stream those hitters and avoid those pitchers.

Here are the HR Park Factor for the top-five and bottom-five stadiums early in 2021 followed by the previous five years of data. These stats come from ESPN. For reference, a rate higher than 1.00 means the park favors the hitter and below 1.00 favors the pitcher.

Obvious takeaways:

• Coors Field is a hitter's park (duh).
• Cincy and Baltimore must be hitter's parks considering how bad those offenses have been the past couple of years.
• Green Monster no likey da long ball
• San Fran winds keep doing their thing to suppress power and always will.

The rest of the home parks on this list, however, are confusing. Some rank high in HR factor one year then go way down the next year. We hear about Comerica in Detroit being among the worst places to go deep yet it was way above league average in 2016-2017 and has spent half the past six seasons over 1.00 which makes it look like a hitter's park for power!

How do some ballparks shift from one end of the spectrum to the opposite? Once a launching pad, always a launching pad, right?

Lost Ones

The biggest mover is Miller Park in Milwaukee. Five years ago, it ranked only behind Coors Field in terms of Park Factor for runs and homers, producing a 1.29 HR Factor. In 2021, it is second lowest with a 0.55 HR Factor. How could one park change so drastically? Does a lack of capacity crowd make that kind of difference? Of course not. It's the lineup, dummy.

The Brewers have spent most of this season without Christian Yelich, who has zero homers on the year. Young slugger Keston Hiura hit one homer along with his .152 average before getting demoted. Ryan Braun isn't around anymore. Let's just admit that the Brew Crew has one of the weakest offenses in the NL. It wouldn't matter if they were playing in Beloit Stadium, they'd still be one of the lesser slugging teams around.

Petco Park in San Diego was long cast as an extreme pitcher-friendly park. In 2016, it had the third-lowest Park Factor. It should be noted that back in 2013, the dimensions were altered to make it play more neutral by moving the fence in left-center and right-center field in 12 feet. Didn't matter - it was still suppressing power. Over the past two seasons, however, it ranks 13th and 16th in HR Factor. What made the bigger difference: climate change or Manny Machado and Fernando Tatis Jr.?

Then take the "Big A" in Anaheim. Five short years ago, back in the Albert Pujols era, the Angels' home park was fourth-lowest in HR factor despite a prime-age Mike Trout in front of Phat Albert. The problem is that nobody else on that squad other than Kole Calhoun and C.J. Cron had any sort of legit power tool. Those four aside, the only other player who reached double-digit home runs that season was Jefry Marte. Next in line was Jett Bandy with eight dingers. Not quite Murderer's Row.

How do you explain Cleveland, which ranks top-five in HR factor for the second time in six years but also has two seasons well below league average? Two big boppers in Jose Ramirez and Franmil Reyes who are among the MLB home run leaders and a pitching staff that has surprisingly yielded 53 taters, ninth-most in the majors.

Home parks are a factor in terms of offensive production in some cases but not always. Aside from the regular outliers, which I'll list below, the best indicator of whether a park will be favorable to home runs in a given season is still the caliber of hitters who take residence in the batter's box.

Nothing Even Matters?

I'm not saying Ballpark factors don't matter at all because it's clear that certain parks will always play favorably one way or the other. It's just not as cut-and-dry as we make it seem.

There's also the matter of handedness for park factors. Some play much better to right-handed hitters than left-handed hitters and vice versa. This is a rabbit hole I don't intend to fall down right now but deeper digging should be done if you plan to in fact utilize park factors in your decision-making process, just as you would with L-R splits and Batter vs Pitcher matchups. By the way, here's a free DFS tip: career numbers for an individual hitter vs. individual pitcher usually mean jack squat.

Those who use park factors as part of their arsenal when making informed choices either on draft day or when building DFS lineups stand validated in one sense: there are certain stadiums that consistently favor power production and those that deter it. Once you escape those few, we shouldn't be so quick to label all others as necessarily belonging in one category or another.

Without further ado, I present the triumphant trio of hitters' parks and pitchers' parks based on my extensive research of looking up park factors online for a few minutes and glancing at the data.

Most Hitter-Friendly Parks: Great American Ballpark (Cincinnati), Coors Field (Colorado), Oriole Park (Baltimore)

Most Pitcher-Friendly Parks: Oracle Park (San Francisco), Tropicana Field (Tampa Bay), Fenway Park (Boston)

Those That Might Fluctuate Year-to-Year: everything else

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