The intentional walk isn’t what it used to be. Back in the day (i.e., pre-2017), when a team wanted to intentionally walk an opposing hitter, the pitcher had to physically throw four balls out of the strike zone. It seems so quaint now. Since 2017, pitchers no longer throw those pitches. The manager simply indicates to the umpire that he wants the batter walked and the batter goes to first.

This simple task of communicating to the umpire that the opposing batter should be directed to first base has been executed by every manager in baseball this season except one—A.J. Hinch. The Houston Astros have not issued an intentional walk all season. Should they finish the year with a zero in the IBB column, in a season when records for home runs hit and allowed are falling left and right, they will own an unbreakable record. You can’t walk fewer than zero.

This isn’t a new thing for the Astros. They set the standing record for fewest intentional walks last year, when they issued just four free passes (note: intentional walks have only been officially tracked since 1955). In 2017, they issued the third-fewest intentional walks of any team. The Astros have been miserly when it comes to free passes in each of the last five years, which is a significant change in strategy compared to earlier in the decade.

As most baseball fans know, the Astros have been one of the best teams in baseball for the last three years, but they endured an ugly stretch of seasons from 2011 to 2013 to get where they are now. During that brutal three-year stretch, the Astros averaged 108 losses per season. They were also generous with the intentional walk. In 2011, they gave out 59 free passes, fourth-most in baseball. They followed that up with 40 intentional walks in 2012, ninth-most in baseball. They’ve steadily reduced their IBBs in the ensuing years, all the way down to zero this year.

Like the Astros, the major leagues as a whole have seen the number of intentional free passes handed out decrease each season. It looks like the trend began right around 2012. This can be observed by looking at intentional walks per nine innings for each decade since it became an official stat in 1955:

0.30 IBB/9 IP—1955-1959

0.33 IBB/9 IP—1960-1969

0.34 IBB/9 IP—1970-1979

0.32 IBB/9 IP—1980-1989

0.28 IBB/9 IP—1990-1999

0.27 IBB/9 IP—2000-2009

0.21 IBB/9 IP—2010-2019

Intentional walks were issued at roughly the same rate for three and a half decades from 1955 to 1989. During this stretch, teams offered up an intentional free pass about once every three games. The rate dropped in the 1990s and 2000s to roughly two intentional walks every seven games. Since 2010, teams have issued intentional walks about once every five games.

The trend has continued in more recent seasons. The seven lowest rates of intentional walks per nine innings have come in the last seven years, with this year’s rate of 0.16 IBB/9 IP being the lowest ever. That rate of intentional walks works out to about one intentional walk per team every six games, which is half as often as it was from 1955 to 1989. In this homer-happy season, where seemingly every hitter can put one over the fence, it makes sense to avoid putting runners on base with the free pass.

For the record, the highest rate of intentional walks in a season was in 1967, when MLB teams issued 0.40 IBB/9 IP. That’s about two intentional walks per team every five games. The Los Angeles Dodgers led baseball with 101 intentional walks and Don Drysdale led the team with 19. He didn’t lead the league, though. Jim Bunning and Ron Willis each intentionally walked 20 batters. By contrast, the 2019 leader in intentional walks (through roughly 88 percent of the season) is Aníbal Sánchez, with 10. No other pitcher has more than seven.

It’s probably not a coincidence that the rate of issuing intentional walks began its recent downward trend just a few years after the publication of The Book: Playing the Percentages in Baseball. There’s a chapter in the book devoted to the intentional walk in which the authors use run expectancy charts and the game situation (score, outs, inning, baserunners, the ability of the current batter and the following batter) to work through when a manager should call for an intentional walk.

The general recommendation is that the intentional walk should be used sparingly. Before considering the quality of hitter due up and the hitter on deck, in every base-out situation, giving the opposing team a free base runner increases the run expectancy. For example, using the run expectancy chart from 2010 to 2015, a team with runners on second and third and one out is expected to score 1.376 runs. Putting the upcoming batter on to load the bases increases the batting team’s run expectancy to 1.541.

Teams have cut down on issuing intentional walks over the last decade, which shows they’re learning. They are likely still issuing too many intentional walks, though. While the Astros have yet to call for a free pass, seven teams have already issued more than 30 intentional walks this year. The Marlins (46), Mets (37), and Nationals (37) top the list.

Those three teams are managed by Don Mattingly, Mickey Callaway, and Dave Martinez, respectively. These are not managers known to be on the cutting edge of analytics. In a recent September game, Callaway called for an intentional walk of Phillies catcher Andrew Knapp to load the bases for Phillies outfielder Bryce Harper, who was pinch-hitting for reliever Mike Morin. Knapp is projected by the FanGraphs Depth Charts to hit .212/.309/.336, a 69 wRC+. Harper is projected to hit.258/.388/528, good for a 132 wRC+. Callaway chose to intentionally walk a hitter who is 31% worse than league average–so his pitcher could face a hitter who is 32% better than league average.

The move didn’t work, as Harper walked to give the Phillies a 10-6 lead in a game they eventually won 10-7. When asked afterward why he chose to intentionally walk Knapp and face Harper (who was pinch-hitting for Morin, remember), Callaway said he wanted to get Morin out of the game. I would guess Morin is a perfectly fine guy, but he’s essentially a replaceable middle reliever, and the Phillies had at least a few guys as good or better than him ready in their expanded September bullpen. It was a mind-boggling move by Callaway.

A Hardball Times Update by Rachael McDaniel Goodbye for now.

Saying the intentional walk should be used sparingly doesn’t mean that a team should never use the intentional walk. It just means that the conditions have to be right for it to be the best strategy. Determining when to use the intentional walk comes down to the elements mentioned above, with the hitting ability of the current batter and the ensuing batter(s) being major factors.

As you might expect, the most likely instance in which an intentional walk is a good idea is when the hitting team’s pitcher is on deck. Pitchers are terrible hitters. They are so much worse than position players that there are times when an intentional walk to the hitter in front of the pitcher is the optimal move.

It looks like this is another area in which teams have improved over the last few years. I calculated the percentage of intentional walks issued to the number-eight hitter in the National League out of the total number of intentional walks issued to all NL hitters since 2002 (as far back as I could find data for at FanGraphs). This is a proxy for how often the hitter batting in front of the pitcher is intentionally walked (with the caveat that sometimes pitchers bat eighth these days). If the number-eight hitter is being intentionally walked more often, that means hitters at the other batting positions are being walked less often.

The data suggests this is what is happening. From 2002-2008, 23% of all intentional walks in the NL were to number-eight hitters. From 2009-2012, this rose to 25%, a modest increase. Since 2013, 29% of all intentional walks in the NL have been issued to number-eight hitters. This year is the highest percentage on record—34%. Teams are getting smarter.

The 2019 Astros are on the extreme end when it comes to intentional walks. They have chosen the simplest option, the anti-Nike slogan: just don’t do it. There’s a good chance the Astros have passed up some opportunities in which the intentional walk would have been the better option, but they seem okay with that.

Another interesting thing about the Astros—the four intentional walks they issued last year were by relief pitchers. When they intentionally walked 17 batters in 2017, 15 were by relief pitchers. The last two intentional walks issued by an Astros starting pitcher came early in the 2017 season, on April 4 (Lance McCullers, Jr.) and April 10 (Charlie Morton).

In the April 10 game, Charlie Morton and James Paxton were locked in a 0-0 tie in the bottom of the fifth. With one out and runners on second and third, Morton intentionally walked Robinson Cano. Then Nelson Cruz hit a single to score two runs and Kyle Seager followed with a sacrifice fly and the Mariners led 3-0 in a game they would eventually win 6-0. It was an intentional walk epic fail. Apparently, that was enough for the Astros and they haven’t called for an intentional walk by a starting pitcher since–460 straight games through Sunday, September 8.

The Astros are unusual in that they don’t intentionally walk anyone, but it’s not unusual that, in the past, they had their relief pitchers give out free passes more often than their starters. This is true for MLB teams going back to 1955. Teams have always had their relief pitchers intentionally walk hitters at a higher rate than their starters. In the 1950s and 1960s, relief pitchers issued free passes a bit more than twice as often as starters. In the 1970s, it was three times as often, which led to a peak of around 3.5 times as often in the 1980s and 1990s before dropping back down to about three times as often over the last 20 years.

This makes sense because relievers are used in late-game, higher leverage situations. When the game is on the line, managers try to gain every advantage in the pitcher-hitter confrontation and the intentional walk is one of their tools. The single-season leader in intentional walks is relief pitcher Gene Garber (24 in 1974), followed by relievers Mike Garman (23 in 1975), Kent Tekulve (23 in 1982), and Dale Murray (23 in 1978).

All four of these relievers were right-handers who intentionally walked more left-handed batters even though they faced more righties. Their managers were looking for the platoon advantage. I know Garber was a right-handed sidearmer and Tekulve was a submariner (like Dan Quisenberry). Tekulve, specifically, was particularly susceptible to lefties during his career (.221/.260/.297 by RHB, .280/.375/.383 by LHB). In the case of Tekulve in 1982, 22 of his 23 intentional walks were to lefties (one every 10.6 plate appearances).

Tekulve also happens to be the all-time leader in intentional walks with 179–two more than Greg Maddux, despite pitching 3500 fewer innings. Tekulve averaged more than one intentional walk every nine innings and the lefty-righty breakdown is impressive—77% of Tekulve’s career intentional walks were to lefties. He intentionally walked one right-handed batter every 85 plate appearances and one left-handed batter every 18 plate appearances.

Tekulve’s manager for much of his career was Chuck Tanner, who was by all accounts a very likable guy. He was considered a “player’s manager” and had particular success with Dick Allen during his White Sox day’s in the early 1970s. Despite how often Tanner directed Kent Tekulve to issue a free pass when he managed the Pirates, issuing intentional walks wasn’t a notably remarkable thing about Tanner’s managerial career. In 17 full seasons as a major league manager, Tanner’s teams finished in the bottom half of their league in intentional walks 13 times. He just really didn’t want Tekulve facing a lefty with the game on the line.

Unlike Chuck Tanner, Houston Astros manager A.J. Hinch has simply disregarded the intentional walk as a strategy this season, at least so far. Houston general manager Jeff Luhnow is supportive, saying, “The IBB has been overused in the past. I’m glad A.J. is on the leading edge of not having to resort to that.”

We don’t know for sure if Hinch will continue to scorn the intentional walk this year. We just know that he hasn’t used it yet. The Astros are currently in a tight race with the New York Yankees for home-field advantage throughout the playoffs. Through Friday, the Yankees were 97-52, giving them a one-game advantage over the 96-53 Astros. Considering the Astros are an AL-best 56-20 at home, it’s clear they would definitely like to have that home-field advantage.

Let’s imagine a scenario in which Hinch is really tempted to issue an intentional walk. The Astros close out their regular season with a four-game series against the Angels in Los Angeles. Say they go into the last game of the season needing a win to get home-field advantage throughout the playoffs. The game is tied through eight innings before the Astros take a one-run lead in the top of the ninth.

In this hypothetical situation, the Angels rally in the bottom of the ninth to put runners on second-and-third with two outs and Mike Trout coming to the dish. Trout is projected by the FanGraphs Depth Charts to have a 175 wRC+. Because of other moves during the game, the on-deck batter is Anthony Bemboom, who is projected for a rest-of-season 55 wRC+. Would A.J. Hinch really pitch to Mike Trout in this scenario?

Because of Trout’s season-ending injury, we will never know. But we do know if the Astros can go another couple weeks without issuing an intentional walk, they’ll have a record that can be tied but never broken.