2016 Park-Factor Update: National League

As the battle for a handful of playoff spots intensifies in both leagues, we today complete our late-season look at MLB park factors. Earlier this week, it was the American League; today, the senior circuit. These park factors, as explained in previous installments, are based on granular batted-ball data, such as exit speed and launch angle.

As a reminder, here’s the quick-and-dirty on the method used to calculate these park factors. Through August 21, 106,962 balls were put into play during MLB regular-season contests. They resulted in an overall batting average of .328 and slugging percentage of .537, while fly balls generated a .328 AVG and .895 SLG. Line drives generated a .661 AVG and .872 SLG, and ground balls a .237 AVG and .258 SLG. (Oh, and pop ups have generated a .018 AVG and .028 SLG.) Each BIP type was split into “buckets” separated by 5-mph increments. The top fly-ball bucket begins at 105 mph, and the top liner and grounder buckets begin at 110 mph.

For each ballpark, the actual production derived from that park’s actual BIP mix was compared to the projected production, assuming that each BIP bucket generated MLB average production for that BIP type/exit-speed combination. Convert everything to run values, and voila, park factors, both overall and by BIP type.

The table below contains the actual and projected production for all BIP (left columns) and for fly balls only (right) in all 15 NL ballparks:

The table above is presented in descending 2016 Park Factor order. Fly-ball park factors for all parks are presented, as they are usually the primary driver of overall park factors. All seven of the AL parks with fly-ball factors over 100.0 had overall factors over 100.0, but there are two exceptions to that rule in the NL: the Mets are close to 100 on both fronts, while good old San Diego continues to confound. Petco Park’s fly-ball park factor seems to fluctuate wildly from season to season, perhaps due to marine-layer variations. This year, Petco’s squelching production in the air, but giving it up elsewhere.

Some key MLB-wide data to keep in mind as we take a park-by-park look at some underlying drivers that made them hitter or pitcher-friendly: 82.9% of all fly balls (20-50 degree launch angles) hit at 105 mph or higher had gone over the wall through 8/21. At 100-105 mph, 48.0% of flies were homers, with the percentage dropping to 15.5% between 95-100 mph and 3.1% between 90-95 mph.

Only 176 line-drive (between 5-20 degree launch angle) homers, or just under six per park, were hit through 8/21. Of liners hit at 110 mph or higher, 11.1% were homers. The mark dropped to 3.7% between 105-110 mph and 0.6% between 100-105 mph.

Without further ado, here are some defining characteristics of the 15 NL parks through 8/21:

Arizona
Chase Field has a reputation as a hitters’ park, and while it does rank as the third-most hitter-friendly NL park in 2016, the role of the Arizona pitching staff in this performance cannot be understated. The projected .369 AVG-1.069 SLG on fly balls and .340 AVG-.584 SLG on all BIP has more to do with the Arizona pitchers than their hitters. While its homer PF (90) is actually below average this year, Chase’s 105 1B, 109 2B and 180 3B PFs more than compensate.

Atlanta
This Freddie Freeman character must be pretty good. Turner Field is a pitchers’ park through and through, with 2016 2B and HR PFs of 76 and 94, respectively. The homer rates on both 100-105 mph (33.9%) and 95-100 mph (9.9%) fly balls are also both well below MLB average.

Chicago
Wrigley Field has yielded homers at exactly the MLB average given its BIP mix, but has squeezed other types of extra-base hits, with 2B and 3B PFs of 92 and 73. A cold, wet spring also tamped down run production early in the season, as discussed in my early-season park-factor piece.

Cincinnati
It’s all about the home run at Great American Ballpark. Hitters “should” have batted .306 AVG-.805 SLG in the air through 8/21, but actually hit .342 AVG-.971 SLG, for a 137.0 fly ball PF that is second only to Coors Field in all of baseball. Great American’s 134 HR PF is a product of hefty 65.5% and 25.3% homer rates on 100-105 and 95-100 mph flies, respectively.

Colorado
Coors is gonna Coors. It inflated all types of hits (101 1B, 126 2B, 201 3B, 114 HR PFs), and saw 55.4% of 100-105 mph and 22.6% of 95-100 mph fly balls going over the wall. In a nutshell, the hardest-hit flies in the game were struck in Arizona, where hitters “should” have batted .369 AVG-1.069 SLG. In Colorado, they actually batted .429 AVG-1.150 SLG in the air. Altitude means business.

Los Angeles
Dodger Stadium has a reputation as a pitchers’ park, but the fences are actually quite reachable in the middle third of the field. Its homer PF is actually above average at 105, though the park deflates all other types of hits, especially triples (56). Homer rates are near average in most velocity buckets, but are well above average from 100-105 mph (54.8%).

Miami
The fences came in at Marlins Park this year, immediately making it a much more neutral run-scoring environment. One needs to use such granular data to see this effect, however, as the most weakly hit fly balls (projected .308 AVG-.772 SLG) and BIP overall (.324 AVG-.498 SLG) in the league were hit here. Homer totals are still depressed, as only 38.8% of 100-105 mph flies had left the yard through 8/21.

Milwaukee
Miller Park remains one of the game’s stealth hitters’ parks. Extra-base hits of all types are inflated here (103 2B, 107 3B, 115 HR PFs), the ball carries whether the roof is open or closed, and the very existence of that retractable roof insulates hitters from the offense-sapping weather conditions that significantly impacted the other Upper Midwest and Mid-Atlantic clubs this spring.

New York
Much like Dodger Stadium, Citi Field slightly inflates home runs (105 HR PF) while deflating other types of extra-base hits (88 2B, 53 3B PFs), slightly deflating run-scoring overall. If you hit it good in the air, you have a better-than-league-average chance of watching it leave (52.8% and 19.5% HR rates on 100-105 and 95-100 mph fly balls, respectively).

Philadelphia
Citizens Bank Park has a somewhat undeserved reputation as a hitters’ park, when in fact it’s just a bit more cozy than the Mets’ or Dodgers’ environs. The home of the Phils inflates homers (113 PF) but deflates doubles (90 PF). The homer rates on both 100-105 mph (54.7%) and 95-100 mph (19.5%) were both higher than league average through 8/21.

Pittsburgh
PNC Park, like Progressive Field in Cleveland, saw run-scoring spike sharply upward this summer as the weather warmed. Interestingly, homers (95 PF, with near-MLB-average HR rates in each velocity bucket) didn’t drive that spike; doubles (105 PF) and triples (159) had more of a role. Another interesting note: through 8/21, PNC Park was the only park in baseball not to yield a single line-drive homer.

San Diego
The year-to-year marine-layer-related fluctuations here are a prime topic for a detailed study of its own. Petco has a pitcher-friendly reputation but has performed quite neutrally this season (103 1B, 102 2B, 93 3B, 99 HR PFs). Interestingly, it has the highest ground-ball PF (130.5) in all of baseball this season, while last season it had the second highest fly-ball PF in the NL. You got me.

San Francisco
AT&T Park destroys would-be homers (67 HR PF), but inflates all other types of hits (103 1B, 107 2B, 167 3B PFs). In fact, a not-insignificant number of those would-be homers actually become triples. Homer rates in the key fly-ball velocity buckets are well short of MLB average, especially in the 100-105 mph range (24.5%).

St. Louis
Generally a pitchers’ park, Busch Stadium has inflated only doubles (105 PF) while deflating all other hits, including homers (85). There are very few cheap homers hit here: only 8.5% of 95-100 mph flies went over the wall, while more well hit ones did so at near-MLB-average rates.

Washington
Here’s a stealth pitchers’ park. Nationals Park has deflated all types of hits this season (97 1B, 89 2B, 95 3B, 98 HR PFs). It’s been pretty neutral to well hit fly balls, with actual homer rates in the fly-ball upper-velocity buckets all near MLB average.