MLB Changes Minor League Baseball’s Rules

Last week, MLB announced that it was implementing several rule changes throughout the minor leagues in 2021. While the hostile takeover of the minor leagues was based primarily on economic factors, the new arrangement allows the league to act unilaterally on other issues as well, including the use of affiliate teams as testing grounds for new rules experimentations. Most of these rules had been proposed at one time or another in the recent past, and the league is spreading the adjustments across the various minor league levels:

  • Base sizes: In Triple-A, the sizes of each base will be increased from 15-inch squares to 18-inch squares.
  • Defensive positioning: In Double-A, teams will be required to position four players in the infield: Each player must have both feet in front of the outer boundary of the infield dirt. In the second half of the season, MLB may also require that teams keep two infielders on each side of second base, though that is not a requirement at the outset.
  • Step-off rule: In High-A, pitchers will be required to disengage the rubber before attempting a pickoff throw; violations will result in a balk.
  • Electronic strike zone: In the Low-A Southeast League, select games (it’s unclear which ones or how many) will use the electronic strike zone first tested in the Atlantic League and Arizona Fall League.
  • Pitch timer: In the Low-A West League, pitchers will be placed on a 15-second pitch clock, which is five second faster than the clock currently used in Double-A and Triple-A.
  • Pickoff limits: Across Low-A, pitchers will only be allowed to step off twice per plate appearance. Any subsequent throw over must result in successfully retiring the runner, or it’s a balk.

With those rules in hand, Brendan Gawlowski and Kevin Goldstein have thoughts.

Base Sizes

BG: The best rule adjustments foster desirable behavior without rocking the boat and I think we have that here. Shaving a few inches between bases won’t dramatically increase the number of stolen bases or infield hits, but any subtle alterations should flow in the right direction. And unlike some of these other ideas, which you can’t help but notice, a slightly larger base will be all but invisible to fans in Section 326.

KG: I mean, really, do you care? Does anyone? Depending on one’s interpretation of the 90 feet being from the center of the base rule, this puts bases two to four inches closer to each other, or roughly 0.2 to 0.4 percent. There’s no big impact on the game, which is likely why it’s being implemented at Triple-A. If anything, this could mitigate some injuries on plays that create traffic around the bag, especially 3-1 groundouts. This is fine.

Defensive Positioning

KG: My head is absolutely spinning on this one. I had a theory, I felt strongly about said theory, and then the data came and punched that theory in the face. My initial reaction was that if teams can’t shift, hitters can sell out for power and focus more on driving balls than making contact, so that while no shifts might increase BABIP, less contact would make it a zero sum game.

Then I found Statcast data the showed whiff rates were actually higher with teams shifted than showing a standard defensive configuration. That surprised me, but it’s also a simplistic conclusion. Left-handed hitters get shifted more and also as a group make less contact, while all power hitters get shifted more as well. Still, looking at individual mashers who are prone to being shifted, such as Joey Gallo and Cody Bellinger, showed a similar trend. Are shifted players swinging for the fences out of sheer stubbornness? Are shifted players just focusing on beating the shift by hitting balls over the fence? If non-shifting defenses really create more contact, the rule change has a chance to achieve the desired result, which is more base hits.

Still, I can’t help but feel that this is suppressing innovation. If offense or defense changes the way things are playing out on the field, I’d rather have the other side make the necessary adjustments. Organic changes in baseball are far better for the game than forced ones. I feel like I could spend a week looking at data without coming to a conclusion on this one. I think it’s fair to be skeptical, but this one actually has a chance to meet its intended purpose. Whether or not that’s a good thing might be the more apt question.

BG: I understand and broadly agree with your perspective on innovation and organic change, and that was my opinion on the shift for years as well. But nearly a decade has passed since the shift came in vogue, and I don’t really like any of the ramifications. I knew that the shift was turning singles into outs. Until reading Russell Carlton’s extremely good work and research, I did not realize that a corresponding uptick in walks more or less cancelled out those benefits.

Perhaps the biggest hurdle to organic innovation here is how the offense has responded: With exceptions like Anthony Rizzo aside, few hitters reacted to the shift by learning to bunt and taking the free base until the defense adjusts back. Instead, of course, they’ve tried to hit over the shift. It’s worked, to an extent, at least in our bouncy-baseball era. But alongside, strikeouts and walks have continued to surge and the league hit .245 last season. Two-forty five!

At the end of the day, batters only have so much control over where they hit the ball, and it may just be the case that hitters are no match for modern fielding data and the note cards fielders carry in their back pocket. If that’s the case, blunt as it is, I’m open to experimenting with a rule that limits how teams can shift. I’ll admit, I’m a little more curious about the effects of limiting the number of fielders on each side of second base, but this seems like a reasonable experiment to conduct. By mandating four players stand on the dirt, you’re allowing the infield to shift in a way that still lets fielders gobble up grounders but no longer allows them to take away the low line drive single to right. I think that’s a good aesthetic tradeoff.

Step-off Requirement

BG: The obvious implication here is that lefties now have fewer tools to hold runners on with. The ability to make a snap throw to first still gives them a distinct advantage over righties — for some southpaws, the quick toss was their better move anyway — but no longer can lefties drift their front foot from the rubber at a 45 degree angle and test the outer limits of the balk rule. Joe Beimel retired just in time.

A little bit of clarity in the balk rule will certainly be nice: I’m all for shades of gray in most things, but I’ve never felt that baseball’s version of the block/charge problem has made for compelling discussion.

I also wonder if this adds a wrinkle to the chess match. Now that runners can safely run on first move from lefties, how do pitchers respond? Can they react quickly enough to pivot to a pitch out if they see someone take off? Even if they can, can catchers get on the same wavelength in time for that to be a viable strategy? And if the answer is yes to both, how can runners use that to their advantage? Perhaps this is all moot in practice, but you can dream on a little game theory here.

KG: I’m all for this, and would be fine with it being implemented in big league games from day one, if only to eliminate the cacophony of 20,000 people in the stands yelling “Balk!” at every good pickoff move.

Electronic Strike Zone

KG: This is coming to the big leagues, whether we want it to or not, and most in the game have set 2023 as the over/under mark. I get the overwhelmingly pro-robot umps movement. We want there to be standards, and we want to get things right. Those are good impulses, but there is no potential rule change that could have a greater effect on the game than this one.

Of course umpires miss some calls, and all of them have slightly idiosyncratic zones, but there is a general understanding at least of what a strike should be, and it’s important to realize that the currently agreed upon strike zone is not the one in the rule book. Balls and strikes are going to look weird for a while, and some pitchers will improve, possibly dramatically, with an enforced electronic zone. Meanwhile, the opposite will be true for those who need to change their approach in terms of location strategy. Just because balls and strikes will be called 100 percent correctly doesn’t mean it will be good for the game, or at least some individual’s games.

BG: Exactly. Certain pitches have been strikes for 100 years and it’ll look very weird if they’re suddenly called balls. I also worry that good pitchers will find a way to exploit the technology in a way we’re not prepared for yet. I’m glad that the league has at least gone slowly on this: an automated zone should be tested extensively before it ever sees a big league park. A full year’s worth of minor league data can only be helpful in assessing the efficacy of this technology. Of all the new rule proposals, this is the one to bring along slowly.

Pitch Timer

BG: The minor league pitch clock has worked so well and does exactly what it’s supposed to do. Pitchers have gamed the system a bit by stepping off but if you curtail their ability to do that, it’s a very effective tool for chopping 10-15 minutes of dead time off of the game.

KG: Put this in the big leagues right now. MLB is obsessed with pace of play issues, and no rule will have a greater impact on that than a reasonable pitch clock. On the same hand, the three-batter rule for relievers has no effect on pace of play and therefore should be eliminated. We don’t need extremes here, but just a simple 30 seconds with two warnings and then an automatic ball would shave minutes off of games in an age where MLB has attempted a variety of short-sighted changes that have resulted in seconds.


KG: I have a friend in the game who has pushed this for years. It seemed crazy at first, but I give MLB credit for a creative end-game solution with the balk or out rule on the third throw. Stolen bases are exciting and exciting baseball is good. I’m a middle aged person with fond memories of the power/speed days of the 1980s, but with everyone slugging these days, the value proposition of the stolen base has dropped dramatically. You’ll never change the value of a stolen base, nor the greater negative impact of getting caught, so to encourage attempts something must be done to increase the chances of success.

This is something that needs to be monitored: There is a fine line between encouraging action on the bases and making it too easy to steal. At the very least, teams will need to recalibrate how they value a catcher’s arm in this new landscape. When electronic strike zones remove the value of framing, that will receive greater emphasis in the future anyway.

BG: Agreed.

I want to finish with an observation about the process here. Baseball is not an easy game to adjust. The sport wears its history on its sleeve, and the audience is well-represented in cranky people who don’t want things to change much (to be clear, I firmly put myself in this category in many ways).

Still, all of these changes are reasonable to at least audition. After testing, perhaps we’ll decide that the pickoff rules are too strict or that the electronic strike zone isn’t quite ready for prime time. But we’ll never learn without trying, and these adjustments could legitimately enhance the pace and aesthetic quality of the game without feeling gimmicky. That’s a difficult balance to strike. I haven’t had many compliments for MLB, but credit where it’s due: These are measured ideas being tested in a sensible manner.

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1 year ago

Totally cool for MLB to test these things out. None are out-and-out stupid on their face.

The closest to me is the lefty pick-off move. This is especially the case if umpires continue to allow righties to step off as they turn simultaneously to throw to first. All of the sudden instead of lefties maybe having an advantage, you could see righties having an advantage in pick offs.

I believe there are other defensive advantages to right handed pitchers and this advantage (the current rule) to lefties only evens those out. Not a fan of this at all. Watching Andy Pettitte pick off guys that weren’t even thinking about stealing a base was magic. No reason to dump a beautiful part of the game.

But these are just tests and hopefully MLB can find less intrusive ways of getting their desired results. It seems pitch clocks would by far be the most effective way of reducing dead time.

1 year ago
Reply to  TKDC

I have mixed feelings regarding the lefty pick-off move. On one hand, it think it is fair that they get a little bit of an advantage. But, I have seen far to many umpires let lefties get away with basically striding all the way to the plate and still throwing to first.

I think my preference would be a line or marking on the mound, between 2 to 4 feet in front of the rubber. once the pitcher’s glove side foot passes that line, they have to go home with the pitch, or it is a balk.

1 year ago
Reply to  TKDC

Regardless of the specifics of the rules – MLB should not have the power to determine the rules of the sport. Baseball needs a governing body for the sport itself – and for the anti-trust exemption to be killed so that that is not yet one more part of the sport taken over by MLB team owners