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Home Run Park Factors Part 2 – (Conversion to a Plus Metric, HRPF+)

In order to display my home run park factors in a way that is much more palatable for the readers, I’ve developed FreezeStats Park Factor for Home Runs (PFHR+) metric. It is used the same way other plus metrics are used such as ERA+ or wRC+. It measures how much better or worse a certain ballpark performs compared to the league average with 100 being average. We know if a player finishes the season with a 150 wRC+, he was 50% better than league average offensively. That’s the same premise behind my park factor metric. A park with a 150+ PFHR+ is 50% better than league average for home runs. 

All ballparks are not created equal, dimensions and irregularities within the same ballpark can vary quite a bit. So, I’ve broken the PFHR+ for each field or direction (Left-field, Center-field, right-field). The focus of directional park factors is important when evaluating a player’s tendencies and batted ball profile. It’s also interesting when looking at evaluating pitchers. I’ll analyze pitchers for my next article with respect to this metric in the next couple of weeks. For this article, I’ll cover nine hitters below who have changed teams. I’ll dive into the park change and what type of power output we can expect, both positive and negative based on the team/park change. 


First, I want to look at an example to help explain the park factors. Yankee Stadium is widely viewed as a great place to hit home runs. Part of this is true and part of it is not. It’s perception more than anything. The Yankees have some massive power bats including Aaron Judge, Giancarlo Stanton, and Gary Sanchez. These guys are mashers regardless of where they hit. As you’ll see below, right-field is extremely favorable for home runs at Yankee Stadium. In fact, it’s ranked number one in all of baseball based on my PFHR+ when compared to all right fields! This explains much of Brett Gardner’s late-career success and Didi Gregorius’s 20+ home run power seasons. These left-handed hitters pulled a high percentage of their fly balls to take advantage of the short right-field dimensions. However, Yankee Stadium grades out slightly below-average for home runs to center and left field respectively. 

The slightly unfavorable left-field dimensions don’t hurt the right-handed sluggers on the Yankees because a 450-foot fly ball is a home run anywhere. It actually helps when looking at Aaron Judge. He’s been hitting more and more opposite-field fly balls, up to 49.5% and 48% each of the last two seasons. His HR/FB% on opposite-field fly balls last season was an incredible 37.8% which was significantly higher than his HR/FB% to centerfield. These Home Run Park Factors+ (HRPF+) bare this out. If you take a look at the table below, you can see that Yankee Stadium has a 146 HRPF+ to right field and just an 83 HRPF+ to centerfield. That means Yankee Stadium is 46% better than league average for home runs to right field but 17% below the league average for home runs to centerfield.

To give you an example of the criteria I’m looking at to determine these home run park factors, here’s a three-year snapshot of right field at Yankee Stadium (NYY) and Oracle Park (SFG), the best and worse parks for home runs to right field respectively.

Venue (Rightfield) HR/BRL% (LHB) Non-BRL HR (LHB) HR/BRL% (RHB) Non-BRL HR (RHB)
Yankee Stadium 88.7% 73 77.4% 52
Oracle Park 48.7% 24 15.3% 8
League Average 73.6% 40 49.7% 13

Based on this information, you can see that both left-handed batters and right-handed batters benefit at Yankee Stadium when hitting the ball to right field and the opposite is true at Oracle Park. This is true based on the percentage of barreled balls that become home runs (HR/BRL%) and based on the total number of non-barreled home runs at each venue. The numbers seem a bit confusing and difficult to digest when displayed like this. That’s why I’ve created HRPF+. If you’re interested in the more granular data, feel free to DM me on Twitter or write in the comments below and I’ll share the Google Sheet.


Introducting HRPF+ (Home Run Park Factors Plus)

Park/VenueTeamLF - HRPF+CF - HRPF+RF - HRPF+
Oriole ParkBAL121134100
Comerica ParkDET1042897
T-Mobile ParkSEA97106103
Yankee StadiumNYY9183146
Rogers CentreTOR110101102
Target FieldMIN978294
Minute Maid ParkHOU13673129
Oakland ColiseumOAK9910184
Angel StadiumLAA8214799
Nationals ParkWSH10212485
Kauffman StadiumKCR886677
Fenway ParkBOS966875
Chase FieldARI1066897
Petco ParkSDP11011291
Citizens Bank ParkPHI11591114
Globe Life ParkTEX91110121
Citi FieldNYM110107105
Guaranteed Rate FldCHW110107113
Coors FieldCOL109134113
Dodger StadiumLAD9815095
Busch StadiumSTL8010581
GABPCIN121132136
Marlins ParkMIA868091
Tropicana FieldTBR1028295
SunTrust ParkATL88100100
Miller ParkMIL91134117
Wrigley FieldCHC10510679
Oracle ParkSFG896557
Progressive FieldCLE87108112
PNC ParkPIT7810596

Notes: Columns are sortable! Data for Globe Life in Texas is no longer valid. A new park will be used in 2020. 

Mookie Betts (OF – LAD) formerly with the Red Sox

Park (Team) LF HRPF+ CF HRPF+ RF HRF+
Fenway Park (BOS) 96 68 75
Dodger Stadium (LAD) 98 150 95

I don’t think people realize how much of a boost Betts could see in terms of his power with the move the LA. It’s important to note that while the left field HRPF+ is essentially the same in each park they play differently. Fenway allows more non-barreled home runs to left field (61 HR to 38 HR) where Dodger Stadium has a higher HR/BRL% (74% to 67.2%). That’s the Green Monster at play. The barreled balls with low launch angles smack off the high wall but balls hit at high launch angles that don’t qualify as barrels sneak over the monster. Right field is also more favorable but Betts does not have good power to right field so I don’t expect a huge boost in power production there.

Enough about left field, let’s talk about where Betts is really going to benefit. He’s going from Fenway where the HRPF+ was 38% below league-average to Dodger Stadium that plays 51% better than league-average to CF! Let’s try to quantify this. Betts has increased his fly ball% to centerfield each of the last five years (36.8% to 42.1%). I fully expect Betts, who has an elite hit tool to take advantage of centerfield. His HR/FB% to centerfield over the last three seasons is about 50% below the league average. However, when looking at his average exit velocity and average fly ball distance on fly balls to center, he falls in the top 30% of the league. That’s Fenway Park holding him back. Based on this information, I’d expect Betts to finish with a better than league average HR/FB% to center in 2020. To give some context, I’d expect somewhere between four and six more home runs to centerfield in 2020. 

Anthony Rendon (3B – LAA) – formerly with the Washington Nationals

Park (Team) LF HRPF+ CF HRPF+ RF HRF+
Nationals Pk (WSH) 102 124 85
Angel Sta (LAA) 82 147 99

Nationals Park plays surprisingly well, especially for right-handed batters, so Rendon takes a hit there. He should see some benefits to center and right field though. His batted ball profile on fly balls is pretty evenly distributed. He hit 23 of his 34 home runs to left field in 2019 with a career-best HR/FB% on fly balls to left field. I expect that number to drop However, he improved his quality of contact on fly balls to center and right, respectively but didn’t see many gains in 2019. So while I expect Rendon to hit more home runs to center and right, it should even out with a decline in homers to left. Expecting a repeat of 34 home runs is probably not wise but 28-30 seems like it’ll be in the cards.


Nick Castellanos (OF – CIN) – formerly with the Detroit Tigers

Park (Team) LF HRPF+ CF HRPF+ RF HRF+
Comerica (DET) 104 28 97
GABP (CIN) 121 132 136

I think the baseball world went nuts when they saw this overlay I Tweeted out including Castellanos’ line drives and fly balls over the GABP. 


It’s absolutely nuts. Some people were counting as many as 30 additional home runs based on the overlay. Obviously, that’s not how this works, plus he’s only playing half his games in the GABP. But, going from Comerica that plays like the worst park for home runs to centerfield at 72% below-league average to a top-five park to center is going to do wonders. Castellanos hit 41.5% of his fly balls to center last year but it’s fluctuated over the years. In the final two months of 2019, he benefited from playing in Wrigley which has a 106 HRPF+ to center, so he already took advantage over the final two months of last season. His HR/FB% has consistently been just under 14% for his career and there’s no doubt in my mind, he crushes that rate within a new career-high. I won’t peg him for a 20% HR/FB rate but would probably project him for something around 18% in 2020. Using his 2019 fly ball total, that would bring him to 34 home runs. 

Marcell Ozuna (OF – ATL) – formerly with the St. Louis Cardinals

Park (Team) LF HRPF+ CF HRPF+ RF HRF+
Busch Stadium (STL) 80 105 81
Suntrust Park (ATL) 88 100 100

I just found out that SunTrust Park had a name change and is now Truist Park. The park remains unchanged otherwise in terms of dimensions, so the park factors should be accurate. Overall, Ozuna will receive a park upgrade but it’s not as drastic as some of the players above. Ozuna was a massive underperformer based on my earned home run (eHR) metric last year, so I think he’s due for some positive regression regardless of his location. The park change just reiterates this point. His 22.1% HR/FB rate last year was the second-highest of his career but his barrel rate, hard hit%, expected metrics, etc were by far the best of his career. The question is whether or not he can keep his elite batted ball metrics for 2020. If he can, he should hit 35-40 home runs across 600+ PA, otherwise, he’s still a safe bet for 30 home runs.


Mike Moustakas (2B, 3B – CIN) formerly with the Milwaukee Brewers

Park (Team) LF HRPF+ CF HRPF+ RF HRF+
Miller Park (MIL) 91 134 117
GABP (CIN) 121 132 136

While Miller Park in Milwaukee is favorable for home runs, Cincinnati is simply the best park in baseball for home runs, as I discussed with Nicky C. Unfortunately, Moose bats from the left side limiting his overall benefit from the park change. Leftfield in the GABP is 30% better than Miller Park and right field is almost 20% better. Believe it or not, the slugger has just seven opposite-field home runs in his career. Four of those seven came last season. He did improve his hard contact on fly balls to left field, so if I was a betting man, I’d expect Mosse to hit more than four homers to the opposite field in 2020. But, where Moustakas makes his money is on pulled fly balls. His HR/FB% on pulled FBs typically sits around 35% but I have a feeling, it’ll push 40% next year. I’m beginning to think that Moustakas can hit 40-45 home runs next year. In fact, I’ll throw down a bold prediction about Moose & Casteallnos totaling a combined 80 home runs in 2020. This is bold because even if I combine both player’s career-high home run totals, we come up with 65 home runs (38 for Mosse, 27 for Castellanos). Combining for 15 home runs above their career-bests is a long shot but I think they have a chance. 

Starling Marte (OF – ARI) – formerly with the Pittsburgh Pirates

Park (Team) LF HRPF+ CF HRPF+ RF HRF+
PNC Park (PIT) 78 105 96
Chase Field (ARI) 106 68 97

Chase Field had the humidor installed before the 2018 season, so I’m not 100% confident in the data. However, one thing is for sure, Marte’s power will benefit to left field and is going to take a hit to center. Unfortunately, he regularly pulls fly balls at a below-average clip. However, he crushes pulled fly balls and line drives to the tune of 97.7 mph over the last two seasons. Those exit velocities on LD/FB put him in company with teammate Josh Bell, Edwin Encarnacion, and Khris Davis. If Marte can modify his approach and pull more fly balls, he could reach a new career-high in home runs. But, with a total of 20 pulled home runs over the last two years and 18 home runs to center, Marte’s move may just be neutral if his approach remains unchanged.

Didi Gregorius (SS – PHI) – formerly with the New York Yankees

Park (Team) LF HRPF+ CF HRPF+ RF HRF+
Yankee Stadium (NYY) 91 83 146
Citizen’s Bank (PHI) 115 91 114

We can completely ignore left field when discussing Gregorius’ power. He has NEVER hit a home run to left field and has hit just nine homers to centerfield. Now, he goes from a park that played 46% better than league-average to right field to a park that’s 14% better than league-average. Now that Didi is more than a year and a half removed from Tommy John surgery, I don’t have any doubts that he’ll enter 2020 healthy. Even in an abbreviated season, he was on pace for just under 30 home runs. The switch in his home park probably leads to three-four fewer home runs to right field. The difference to centerfield is about 3% in terms of a three-year HR/BRL%, so that’s relatively minimal. If Didi is a 25-homer hitter in New York, he’s a 22-homer guy in 2020 in Philly.

Avisail Garcia (OF – MIL) – formerly with the Tampa Bay Rays

Park (Team) LF HRPF+ CF HRPF+ RF HRF+
Tropicana (TBR) 102 82 95
Miller Park (MIL) 91 134 117

Let’s see, 11% worse to left field, 52% better the center, and 22% better to right. Is this not enough for you to buy into Garcia who reached 20 home runs for the first time in 2019? He actually earned 28 home runs based on eHR last year, so if he can maintain his impressive quality of contact, he’s a bargain in 2020. He’s notoriously a heavy ground ball hitter but as I highlighted in my potential power breakouts article on Pitcher List, Garcia has decreased his ground ball in four straight seasons. It’s interesting to note that Garcia doesn’t pull many of his fly balls. Will you look at that? Miller Park plays a little less favorably to left field. It’s almost as if the Brewers saw an advantage others didn’t. Nearly, 86% of his fly balls last year went to center or right field. Here’s the spray chart from last year overlayed at Miller Park.

Miller Park plays very favorable to LCF and RCF. I feel very strongly that Garcia improves significantly on his HR/FB% from 2019 and if given 550+ PA, he should hit 25 homers.



C.J. Cron (OF – DET) – formerly with the Minnesota Twins

Park (Team) LF HRPF+ CF HRPF+ RF HRF+
Target Field (MIN) 97 82 94
Comerica (DET) 104 28 97

Let’s address the elephant in the room. Cron’s move to Comerica Park is going to kill any power he has to centerfield. Not that Target Field was all that great for fly balls to centerfield but if you remember, Cron played for the Angels prior to 2018. We now know that Angels Stadium is a homer haven to centerfield. While Cron boosted his barrel rate and hard hit% in 2019, he’s trending in the wrong direction in terms of the percentage of pulled fly balls. His pulled FB% has dropped the last three seasons from 32.7% in 2017 to 24.2% last year. He’s going to want to adjust his approach back to the 2017 version of himself to take advantage of Comerica’s most favorable part of the park, left field. His range of outcomes in terms of home runs is huge. Fortunately, he should play every day because he’s basically the Tigers’ best hitter (at worst, second-best). If his pulled fly ball rate continues to drop and his fly-ball rate to center jumps to 40%, he could end up with a home run total in the low-20s. If he gets back to his pull-heavy approach, I could see him reach 30 home runs with the potential for even more.

If you prefer the color-coded version of the HRPF+, it’s below. Although, it’s not sortable like the table above.

Follow me @FreezeStats. Check out my work at FantasyPros and Pitcher List.





Photo Source : MLB and Lou Spirito