Stats people and sabrmetric followers have a long history of not really like the RBI stat. Most people probably realize now that getting big numbers in RBIs has as much to do with being in the right spot in the batting order, and getting lots of opportunities with runners on base as it has to do with any particular skill at hitting. At least that’s how the theory goes. But what if we really wanted to know which players are best at driving in runs? You could look at splits like OPS with runners in scoring position, but OPS doesn’t consider a sacrifice fly to be a positive contribution, even though there are most likely some cases where batters step to the plate trying to hit a long fly ball, that will at worst be a sacrifice fly. I like the idea of trying to measure how successful the batter is at the thing the batter is trying to do, and I think driving in runs is one of those things a batter is trying to do more often than not. OBP measures what batters are trying to do some of the time. Slugging percentage usually doesn’t, or more batters would be trying to stretch hits into doubles and triples.
So how can we measure how well batters drive in runs after we already know some batters get a lot more opportunities than others? It’s not that big a mystery – measure the success against the opportunities. For example, Buster Posey had 20 plate appearances with no outs and a runner on third. The runner on third scored as a result of 16 of those plate appearances. That’s the most in both those categories. Obviously he never would have driven in 16 runners from 3rd base if he hadn’t had 20 opportunities, but how often does a runner on third score league wide? 53.9% of the time. There were 2709 plate appearances in 2012 with a runner on 3rd and no outs, and the runner on 3rd scored on 1459 times. So if average batters had been in those positions 20 times, instead of Buster Posey, only 10.78 runs would have been driven in from 3rd. So Posey was 48% better at driving in runners from third than the league average.
Using that same method, we can put an expected RBI value on each runner on base for every plate appearance for every batter. Add up the RBIs, add up the expected RBIs and divide actual by expected to see which batters are the best at driving in runs. (Ignoring the scoring decisions where the runner scored with no rbi awarded, because that just confuses things)
Here are the weights for each runner, based on what actually happened in 2012:
|Outs||Batter||Runner on 1st||Runner on 2nd||Runner on 3rd|
As you can see, batters scored on about 3% of plate appearance regardless of how many outs there were in the inning, and the number of outs don’t matter much to how often runners on 1st score. But runners on 2nd base have a slight advantage with 2 outs, and runners on 3rd obviously score less often with 2 outs because the sacrifice is no longer an option. To get the expected RBI for each plate appearance, just got to the right number of outs, and add up the value in the chart based on what bases have runners. Batting with 1 out and none on base gives a value of .026. Batting with no outs and runners on 1st and 3rd gives an expected RBI value of .618. If we add those all up for a player’s entire season, we can see who had the most opportunities to drive in runs.
You probably won’t be shocked to hear that Miguel Cabrera finished first in expected RBI in the American League – the situations he batted in this year add up to 88.38 from the base runner values above. Basically, if an average batter hit in all the situations Cabrera hit in this year, the average batter would have driven in about 88 runs. But Cabrera drove in 139 runs, so he was about 57% better at driving in runs. His RBI/eRBI is 1.572.
On the other hand, Hunter Pence finished first in expected RBI in the nation league, with 94.1. Pence batted with 541 runners on base during his plate appearances, and 281 of them were in scoring position. Cabrera only had 248 runners in scoring position when he batted. And the results for Pence were only 105 actual RBI. His RBI/eRBI is 1.116, telling us he’s only 11.6% better than average for driving in runs. But he’s still above average. Pence’s world series teammate and playoff hero Marco Scutaro wasn’t quite so effective in the regular season. His plate appearances add up to 80.5 expected RBI, but he only drove in 74 runs. That puts his RBI/eRBI at only 0.920. But he made up for it in the postseason.
RBI/eRBI is kind of a weird thing to write – and since I already have home-made stats named Bacon, SPAM, HAM, and PORK, it’s only logical that this stat be name Spare Rib to fit into the suite of sabermeatrics.
Anyway, here’s this 2012 Spare Rib leaders for players with over 500 plate appearances:
|Batter||Actual RBI||Expected RBI||Spare Rib|
|Alejandro De Aza||50||53.206||0.94|
You can see right in the middle there, it turns out Jason Kipnis is that average batter I was talking about above. The runners on base when he batted scored at pretty much exactly the same rate as the major league average.
It turns out managers are pretty good at getting their players who are best at driving in runs into the middle of the order – here’s what the Spare Rib totals look like by batting order position:
4th – 1.154
3rd – 1.138
5th – 1.114
6th – 1.002
7th – 0.969
2nd – 0.931
8th – 0.837
1st – 0.831
9th – 0.652