Two-Year Minor League Park Factors And Team Run Contexts For 2021-22

Ballpark effects loom large in the evaluation of minor league players.

Whereas big leaguers play in a more standardized array of MLB venues and run environments with a stable competition level, the same is not true for minor leaguers.

In the minors, playing conditions vary widely from league to league. The classic example can be found at Low-A, where last season the average Florida State League team scored 4.62 runs per nine innings and the average California League team scored 6.07, making them the lowest- and highest-scoring leagues in affiliated baseball.

But you wouldn’t necessarily know that from examining park factors. Fort Myers in the FSL and San Jose in the Cal League had neutral park factors last season—meaning that those teams scored runs as often at home as they did on the road. It’s just that neutral means something entirely different in each league.

Fort Myers games in the FSL averaged about nine runs scored plus allowed. San Jose games in the Cal League saw nearly 10.25. Over a 130-game season that equates to a difference of more than 162 runs.

So park factors are great for placing players’ performance in a league context, but they’re terrible at placing leagues in context. To get a handle on that, I use something called team run context (TRC).

Team run context is simply the league rate for runs scored per nine innings adjusted by the team park factor for runs scored. This represents the average R/9 rate of a team’s games, counting home and road results. All 120 parks can then be ranked and assigned percentile scores (TRC %tile).

Because baseball has had stability in the minor leagues the past two seasons in terms of affiliations, levels, leagues and parks, I combined both 2021 and 2022 data to smooth out the volatility of smaller samples. Please note that the 2021 season started a month late and does not include April data.

The end result is that the Athletics’ Triple-A Las Vegas affiliate has a 6.66 TRC in its games, the highest rate in the minor leagues and a higher factor than Coors Field—by more than a run. The Braves’ Double-A Mississippi affiliate is at the other end of the spectrum with a 4.55 TRC.

Note that the R Mult column is the two-year park factor multiplier that can be applied at the league level. This value is a comparison of home and road data in a given league. It does not represent an overall minor league context.

Minor League Team Run Context • 2021-22 Combined