When I’m watching baseball, I’m almost always also on Twitter. Twitter has made watching a game by yourself in your home a social experience, and so now, it’s almost like watching a bunch of games with a bunch of other people. It’s great. Twitter is really an amazing creation, considering that the idea is basically mass text messaging.

Among the people I follow on Twitter is Keith Law. Keith is a prolific tweeter, and he interacts with his massive audience pretty much every night. An ongoing point of this conversation between Law and his followers is a derision of the intentional walk. Seemingly every night, someone will send Law an example of a manager putting a batter on, followed by the guy behind the IBB’d hitter launching a bases clearing extra base hit, scoring everyone including the guy who just got walked. Or the pitcher, now without the safety net of having a base open, will end up walking the next guy unintentionally, occasionally forcing in a run without ever forcing the opponent to swing the bat.

Just based on the data that shows up in my Twitter feed on a nightly basis, it feels like the average hitter bats .950 and slugs 2.500 after the guy in front of him gets walked intentionally. And, you frequently hear announcers talk about the disrespect the IBB is showing to the on-deck hitter, and how that might motivate them to prove the opposing manager wrong. All of this talk led me to realize that I actually had no idea what really happened after an intentional walk was issued, but I wanted to find out if the narrative held up to the light of data.

So, as is my usual approach now, I asked Jeff Zimmerman to run a complicated query for me, and now I’m going to take credit for his hard work. Jeff was kind enough to extract the play-by-play data following an IBB, and then removed all of the situations where the next batter was a pitcher, since I don’t think too many people have problems with an intentional walk that forces a pitcher to swing the bat. What we really want to know is how often an intentional walk to get to a worse hitter, or to gain the platoon advantage, ends up working out.

The answer? More often than you might think.

Since the start of the 2010 season, Jeff’s data returned 2,955 plate appearances by position players following an IBB. There have been more intentional walks than this during the last 3+ years, but many of them led to pitchers hitting, and some of them resulted in plays that don’t really fit our criteria, such as a caught stealing or a pickoff. With almost 3,000 IBBs where the play involved the next batter, I think we have a decent sample with which to evaluate the post-IBB outcomes.

Okay, so, what is the overall batting line for hitters following an IBB? Not that impressive, honestly.

PA BB% K% BABIP ISO BA OBP SLG 2,955 9% 19% 0.269 0.141 0.242 0.317 0.382

In all situations with baserunners on, the average line for all major league position players since 2010 is .267/.339/.417, so post-IBB hitters perform worse than hitters who come up in similar situations where an IBB was not involved. In some ways, this should be expected, because the guys who get intentionally walked are usually the best hitters in the game, so the pool of hitters that gets to bat after an IBB is selected for their lack of intimidation. Major League managers are essentially trading an extra baserunner for the right to get to face a worse hitter, and if the overall batting line was higher than the average with men on base, they’d essentially be making that trade-off with no benefit.

This result is needed for the IBB to be a useful strategy, or else MLB managers would be simply giving away runs. Just based on this very simple comparison, it does appear that there is a benefit received from issuing intentional walks, as the production of the next hitter is indeed lower than the league average in those situations.

Of course, nothing is ever that simple. 25% of the intentional walks issued since 2010 have come with a runner on third base and less than two out, so the post-IBB hitters have been hitting in situations where the marginal difference between a hit and a fly out is smaller than it is in most situations. You could make a case that post-IBB batters were incentivized to hit the ball in the air, thus increasing their odds of making an out, because a sacrifice fly is considered a positive result for most batters. Perhaps the base/out states that induce IBBs also create a lower expected batting line?

It’s possible, but the data seems to suggest otherwise. Last year, for instance, Major League hitters hit .316/.351/.478 with a runner on third and zero or one outs, while they hit just .230/.333/.364 with a runner on third and two outs. The same is true in any year you want to look at; Major League hitters hit better, not worse, in sacrifice fly situations. That’s probably because the population of pitchers who allow runners to get to third with less than two outs is worse than the population of pitchers who don’t allow that runner to get there until there are two outs and because the infield will occasionally play in when there’s less than two outs and a runner on third. Those effects seem to outweigh any sac fly attempt bias that would bring down a batter’s line in those situations. Tom Tango points out the real reason; it’s because a good number of outs in those situations don’t count as at-bats, since they’re classified as sacrifice flies. That should have been obvious. Whoops.

And, to be honest, there aren’t that many post-IBB sacrifice flies to begin with. Out of the 2,955 PAs we are looking at, only 138 of them (4.6%) resulted in a sacrifice fly. The intentional walk is not usually followed by an intentional fly out, so I don’t think we can blame that effect for the lowered offensive performance we see from hitters following an IBB. The most obvious culprit is that managers are issuing an intentional walk in a situation where a poor hitter is due up, and poor hitters are less likely to drive in runs than good hitters. And when an IBB is issued and a good hitter is due up, they almost always are facing a same-handed pitcher, and often times a same-handed reliever.

There are certainly times when the IBB does backfire, and I wouldn’t use this data to suggest that the IBB is always the correct decision. There is a real cost to giving the opponents an extra baserunner, and there needs to be a substantial increase in likelihood of getting an out in order to offset the larger potential for an extra run to score from giving the opponent a free baserunner. However, I do think the data suggests that IBBs do serve a strategic function, and can reduce the odds of giving up a run in a situation where preventing one run is of the utmost importance.

For those interested, here’s the matrix of outcome rates after an IBB forces a position player to bat (where Other is a catch-all for things that happened less than 1% of the time, such as triples and triple plays):