Run Expectancy per half inning: 0.505 runs
This table explained:
- The above numbers indicate the net run expectancy added by each Seattle Mariners player, during their 4-13-2010 game with the Oakland A's, as a hitter, pitcher, fielder or baserunner. Total Net Runs are listed in the first column.
The run expectancy on which these numbers are based is derived from a composite MLB average of 2005-2009, recent years weighed more heavily, and park adjusted to the home field (Safeco Field).
Average is 0.000. Any positive number indicates runs above average, and any negative number indicates runs below average.
- You can estimate a pitcher's expected ERA for an outing by taking the run expectancy for Safeco Field (0.505) and multiplying it by his innings pitched, then subtracting the pitcher's pitching Net Runs to get the number of runs that pitcher was expected to allow with his performance. Figure his Runs/9 accordingly and then multiply that by 0.927 to get his Expected ERA.
Doug Fister's expected ERA, for example, is 3.56.
0.505 x 8 IP = 4.040 - 0.622 pitching NR prevented = 3.418 expected runs
3.418 ExpR in 8 IP = 3.845 ExpR/9 ----> 3.56 ExpERA
Fister did allow zero runs in the actual game: His defense (which includes the 0.248 runs Fister saved with his own fielding) prevented the 3.418 runs he would have allowed on average.
- The SEA Luckbox column indicate events beyond the team's control that benefited the team, such as errors and wild pitches.
- Mariners manager Don Wakamatsu is included for decisions such as sacrifice bunts and intentional walks, which in most cases take matters out of his players' hands but also influence the team's run expectancy.
For fun, here's Oakland's Net Run chart: