All your bases be long by us: Examining MLB’s new base size

One of the things that amazes me about this job is I learn things about baseball that, I feel like I should have known, but I didn’t. For example, of course I knew the basepaths were 90 feet, but I didn’t realize it was 90 feet to the far side of the bag — that is, the basepath is 90 feet from the top right corner of the plate to the back line of the first base bag. That’s the crux of MLB’s bet on bigger bases.

The base used to be a 15” square, but for the 2022 season, we’re moving to an 18” square, with the idea being that a larger base incentivizes contact and motion on the basepaths; a runner has less distance to travel to advance safely to the next base, so they’re more likely to do it. The math we’re about to do is slightly complicated by the fact that Americans can’t handle the metric system, but I digress.

All baserunning is a math problem — a runner attempting to steal second will get there in x seconds, it will take the catcher y seconds to receive and throw the ball to second, and the fielder z seconds to apply the tag. If x < y+z, the runner will be safe. If not, the runner will be out.

Average footspeed in MLB is about 27 feet per second, which means it takes about 3.3 seconds to run the entire 90 foot basepath. Of course, the runner doesn’t have to run all 90 feet, they only have to make it to the front side of the bag, which used to be 88’9” away, and is now 88’6” feet away. We’re gonna go down to inches just to make our math a little easier.

So, runners are moving 324 inches per second on average, and with three fewer inches they need to travel, how much of a difference does that make on their splits?

So we are shaving off some time on these splits, but just a little bit. It’s pretty difficult to manually measure 0.0002 seconds of difference, but that is the bang-bang play at first. 30 percent of all challenges from 2018-2020 were that exact play, this kinda thing. You don’t even have to be that fast, go back to the 2018 World Series, Steve Pearce is the victim of a bang-bang call at first base that would be an obvious hit with an inch or two less distance to travel.

Giving the runner these extra 3” means that virtually all of these plays will become hits again, adding about 240 hits a season to the MLB cumulative total — 430 or so challenges a year, with a slightly-less-than-50 percent chance at calls being overturned. This is a marginal effect, the leaguewide batting average would rise literally one point by adding in all those “new” hits, but I’m really interested in the second and third order effects.

First of all, we’re now creating a new class of bang-bang plays. Any play where the runner is clearly out, but out by the proverbial “half a step” becomes considerably closer with 18” bags. Should you have an infielder that double or triple clutches — not that the Yankees would ever have that problem, of course — the play becomes closer still, meaning you’re incentivized as a defending team to have cleaner, more fundamentally sound infielders.

I also wonder if infield deployment will be different. Fielders will have slightly less time to make a play, and they might compensate by playing slightly more in. Of course, the closer to the plate you are as an infielder, the less time you have to react to the ball, and this is particularly true on hard-hit grounders, meaning I think it’s at least plausible that we see a few more groundballs sneak through for hits with larger bases as well.

This isn’t a revolutionary shift in the game, and any hits that do come out of larger bases are going to be on the margins. But if baseball is concerned with creating a more exciting onfield product, it’s going to need “nudges” like this — small interventions that incentivize larger, more structural decisions. Fielders will need to be quicker and more athletic, hitters will have slightly more reason to put the ball in play. You might not notice it on any one individual at-bat, but those extra 3” are going to lead to real changes in 2022.