BRIG (Batters Rate Index Grades) is a "report card" that provides park adjusted/league relative A+ through F grades for the rate statistics that characterize batting performance.The BRIG grades are derived from park adjusted, league relative statistics for batters. Statistics are park adjusted to even out the differences that result from hitting in a shooting gallery like Coors Field versus hitting in a graveyard like the Astrodome. Statistics are league relative to balance out differences in league pitching and year to year offensive levels.
- Using play-by-play data, the outcomes of each player's plate appearances (strike out, non-strike out, walk, single, etc.) are split by game site.
- The plate appearance outcomes for each location are adjusted by the specific park factors for the specific location for each player. The adjusted splits are then combined for each player.
- A pool of regulars is formed for each league. The pool selection criteria is based on plate appearances (PAs). The players in each league are sorted by number of PAs. The lowest number of PAs in the first N players in each league becomes the minimum number of PAs for a regular. In the AL, N is 9 times the number of teams in the league. In the NL, N is 8 times the number of teams in the league. Typically for a full 162-game season this works out to be ~300 PAs.
- The park adjusted batting rates (AVG, OBP, SLG, ISO, HR/PA, BB/PA, SO/PA, KBB, RC25, and SER/PA) are calculated for each batter.
- The mean and standard deviations for each batting rate are calculated for each league using the pool of regulars for each league.
- The batting rates for each batter in each league are converted to the number of standard deviations from the league mean.
- The standard deviations for players who have changed leagues during the season are combined (weighted by the number of PAs in each league).
- The combined deviations for all players (both leagues) are sorted by descending SER.
- Grades are assigned according to the following scale:
Grade Deviations from Mean A+ 1.50+ A 1.25 A- 1.00 B+ 0.75 B 0.50 B- 0.25 C+ 0.10 C -0.10 C- -0.25 D+ -0.50 D -0.75 D- -1.00 F -INFINITY
SER is calculated from Thorne & Palmer's base runner/out expected run matrix. SER measures the net change in expected runs that the (park adjusted) outcomes of a player's plate appearances will cause versus a marginal frequency distribution of baserunner/out situations.The player's net expected run change would be:Still with me? Let me clarify...
Consider the most common baserunner/out case, bases empty 0 outs, and a batter who in 550 plate appearances made 350 outs, 50 walks, 95 singles, 25 doubles, 5 triples, and 25 home runs. State transitions in the matrix will be as follows:
PA Outcome New State Out Bases Empty; 1 out Walk Runner on 1B; 0 outs Single Runner on 1B; 0 outs Double Runner on 2B; 0 outs Triple Runner on 3B; 0 outs Home Run 1 run scores, Bases Empty, no outs
350*ER(Bases Empty;1 out) + 50*ER(Runner on 1B;0 out) + 95*ER(Runner on 1B;0 out)+ 25*ER(Runner on 2B;0 out) + 5*ER(Runner on 3B;0 out) + 25*(1 + ER(Bases Empty;0 out)) - 550*ER(Bases Empty;0 out)The average batter will see the bases empty, 0 outs case 23% of the time. The net expected runs from this case,therefore, will be weighted by 0.23 when summed with the net expected runs from the other cases.
After the weighted sum of the net expected runs from all the baserunner/outs cases, the result is divided by the number of plate appearances to get SER/PA.
What is BRI?
BRI is a numeric representation of the SER standard deviation grade. League average is 1000 which corresponds to a grade of C.