Let’s Consider a Few More Questionable Intentional Walks
Last week, I wrote about some intentional walk decisions that merited further scrutiny. One of them was pretty bad and one of them was a little bad, but both managers advanced to the NLCS — and now, like clockwork, we have more intentional walk decisions to analyze. Playoff baseball is predictable like that, even as it’s unpredictable in other ways.
Let’s take these two chronologically. The Yankees had their backs against the wall, down 2-0 against Gerrit Cole to start the seventh. It got worse quickly, with two of the first three runners reaching base. That gets us to our situation; second and third, one out, and Alex Bregman at the plate facing Adam Ottavino. Aaron Boone put up four fingers; he chose to face Yuli Gurriel rather than Bregman.
The surface level math on this one doesn’t look that bad for Boone. The trail runner here simply doesn’t matter that much; if Bregman scores, it’s 5-0, and three innings to score five runs is a tall task against Gerrit Cole and the best relievers the Astros can muster. To approximate the lower run-scoring environment they’re facing, I lowered the run environment in our WPA Inquirer to 4.5. The decision hardly hurt the Yankees; their odds of winning fell from 12.3% before the walk to 12.0% afterwards.
When an intentional walk only costs 0.3% of win expectancy when ignoring batters, it’s more often a good one, and a cursory look at Bregman and Gurriel’s wOBA agrees with that. That doesn’t even add in platoon splits; Gurriel has a reverse split in his major league career, and even regressing it back to the mean leaves him only 3% better against lefties than righties. Bregman, meanwhile, clocks in at 6.8% better against lefties than righties post-regression.
Put that all together, and Gurriel’s projected wOBA against Britton (accounting for Britton’s own splits) comes out to .314, while Bregman’s is .372. Given that the Yankees gave up so little win expectancy by putting Bregman on, the back-of-the-envelope math makes the decision obvious. The team would need to face a batter who projected to be at least 31 points of wOBA worse than Bregman to make the decision worth it, and Gurriel is 58 points worse. Good intentional walk! Read the rest of this entry »