MASTER NOTES: BDIs

I don’t know if you saw the recent story at MLB.com by Anthony Castrovince, in which he held a straw poll of 35 players to ask which stats players like—and don’t like.

The winner for hitters was OPS, with 10 votes of the 35 cast. OBP was second, with six votes. Then ... RBI, with five.

All right, with 35 votes, this was well short of a representative sample. But still. RBIs?

Luckily, some players are recognizing the obvious weakness of the RBI as an individual stat. TOR C Russell Martin commented, “Not everybody has the same opportunities in a year. I wish there was a better stat for the percentage of baserunners driven in." To which the great baseball researcher Mitchel Lichtman tweeted: “Hmm, how about, say, (percentage) of base runners driven in?"

Russell Martin is on my Tout Wars-AL team, and has not been especially productive this season, in RBIs or anything else. So I thought I would look into his question, just in case it is nagging him into his current malaise.

First, some notes about what we’re looking at—and what we’re not. In particular, we’re not looking at RBIs, which are scoring decisions. We’re looking at Baserunners Driven In (BDI), which includes some baserunners who cross the dish without the benefit of RBIs (scoring on errors, for instance, or scoring on double plays). As well, we’re not counting the RBI a player gets from hitting a home run, since he gets his own RBI irrespective of the runners-on situation. Of course, I am counting the BDI as the result of homers. And BDIs and RBIs are going to be pretty closely aligned since about 96% of runs scored are credited as RBIs.

Let’s start with the game-wide numbers. According to the database at baseballsavant.com, through the games of Wednesday, May 9, major-league hitters had come to the plate with runners on about 43% of the time. The hitters drove in about 20% of them.

Naturally, the issue is more complicated. It matters quite a bit where on the bases the runners were. The best situation to drive in a run was with a runner on third. That makes sense, since a runner can score from third on any base hit, sac flies, fielder’s choices, and errors. By contrast, a runner can score from first only on extra-base hits.

Anyway, when it’s all added up, the situations with the highest rates of driving in at least one run are:

  • Runner on third (48%)
  • Runners at second and third (27%)
  • Runners at first and third (26%) and
  • Runner at second (25%)

The rate of total runners scoring is in the same order, and of course, the single-baserunner situations have the same likelihood of scoring. As we’d expect, though, more runners score when more runners are aboard:

  • Runners at second and third (40%)
  • Runners at first and third (31%)

Oddly, bases loaded is only 16% of run-scoring events and 26% of runners scoring, the added runner at first more than offset by the increased numbers of force-outs and double plays that wipe out advancing runners, thwart rallies and end innings.

It’s too early in the season to parse individual players’ expected BDI (xBDI), since most of them have only a handful of any particular baserunner situations. That said, however, it seemed reasonable to see how players stack up in having the combined high-RDI situations, second, third, second-and-third, and first-and-third. That way, we can check to see if Russell Martin is getting shafted in some way.

Looking only at players with at least 80 PA this season, the average batter has had about 21% of his PAs in the premium BDI situations. The league leader in premium PAs is BOS 3B Rafael Devers, who has come to the dish with those highly scorable runners 38% of the time. Also at 33% or higher:

  • Robinson Cano
  • Javier Baez
  • Carlos Asuaje
  • Jean Segura
  • Matt Adams
  • Denard Span

Most of these top opportunists have driven in runners proportional to their opportunities, although Baez, Segura, and Span are well ahead of their expected pace.

At the bottom end, seven hitters have come to the plate with premium baserunners fewer than 10% of the time:

  • Ian Kinsler
  • Pedro Alvarez
  • Gregory Polanco
  • Bradley Zimmer
  • Miguel Rojas
  • Josh Donaldson
  • Yoan Moncada

Again, all of these hitters have low BDI numbers in line with their paltry opportunities. (And here’s a news flash for you: also among the bottom dwellers are stars Mike Trout and Mookie Betts, so there could be some BDI improvements, and RBI gains, coming if their teammates can do a better job getting on. Of course, both hitters, and some of the others on the tail-end list, have been at or near the top of their batting orders this year, so the wait will be for the 8-9 hitters to get aboard.)

Oh, and I’m sure you’re wondering: What of Russell Martin? Martin is, indeed, a little under the norm, with just 18% of his PAs coming with premium baserunners aboard. He is getting fewer chances to drive in runs. That said, his teammate Justin Smoak is also at 18%, and he has driven in eight runners—ahead of expectations. Martin should have driven in four, but has only one.

I don't know what to make of all this. But I am sure that Russell Martin will start driving in runs like crazy. I hope so. I could use the help.


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  For more information about the terms used in this article, see our Glossary Primer.