What are the chances the Yankees have a historic home run chase?

I’ve never liked the expression “chicks dig the long ball.” Aside from it’s cringey assumption that all women are “chicks” and all like the same things, as some sort of mass collective that all share the same wishes and desires, it also ignores the other half of the population that digs the long ball.

Baseball fans, by and large, love home runs. Front offices do as well. The home run is the most efficient way to score runs, and similar to basketball’s three-point revolution, dingers are becoming the foundation of an offensive approach. In the NBA, teams are maximizing shots taken beyond the arc, since three-point shots have about the same likelihood as two-point attempts outside the paint. More three-point attempts mean more made three-pointers, mean more total points. In the same vein, more players attempting to hit home runs means more home runs, means more total runs.

Coming into 2018, the Yankees had assembled one of the most prodigious offensive lineups in my lifetime. Brian Cashman acquired the NL MVP, adding him to a lineup that featured the AL MVP runner-up, the best hitting catcher in baseball, and now the best hitting shortstop in baseball. Dong lovers everywhere began salivating at the thought of what this team would do to baseballs, and how close they would come to the 1997 Seattle Mariners record of 264 home runs in a single season.

We’re now approaching a month of baseball, and the Yankees have played 25 games through Friday night’s win over the Angels. At the beginning of the season, most projection systems believed the Yankees would eclipse that 264 HR total, so I thought we should check in on the chances they do so.

So, I engaged the help of my much smarter, more successful and more attractive girlfriend, who is much better at statistics than I am, and we built a probability model to track just how close the Yankees were keeping to a record HR pace. Thank you Marie, you are very cool and everyone on PSA should congratulate you on completing your Master’s this semester.

Projections are a median possible outcome, or in other words, represent that which a team has a 50% chance of accomplishing. 25 games in, the Yankees are close to holding serve on their projection, with about a 43% chance of breaking the single-season home run record:

So, what does this readout tell us? The Yankees top the class in home runs per game, with the Angels and White Sox well behind in second place, averaging 1.42/game. The standard deviation for New York is also small relative to the league, which means the Yankees tend to be fairly consistent in the number of home runs per game. This makes their season totals a little easier to predict, since we can be relatively confident they’ll hit about the same number of dingers every day.

Extrapolating these numbers into a full season means we have to borrow a bit from the 2017 league-wide home run pace. Of course, last season saw more home runs than any other season in the history of the game, but like I explained above, this is a trend across all teams. It’s not unreasonable to assume that we’re only going to get more home runs, so using the trends of last season work well here.

Combining the Yankees’ production to this point in the season with the historic HR numbers from 2017 gives us a pretty fascinating distribution of possible outcomes. The Yankees are guaranteed to end the season with 40 home runs, as that’s what they’ve logged through the first 25 games. The distribution of possible outcomes gives a median - what FanGraphs’ would call projection - of 259.2 home runs, just short of the Seattle record. Visually, that looks something like this:

Our vertex here shows the pace the Yankees are currently on, and that shaded area reflects that 43% chance of a record season. If you prefer cumulative distributions, well, I’ve got that for you too:

The most fun part of this whole distribution is, if the Yankees really turn it on through the rest of the season, it’s not outside the realm of possibility that this team hits 300 home runs. Right now, there’s about an 8% chance that happens.

The last point to make here, is that there’s pretty good evidence that that median outcome, 259.2 home runs, is going to change over the season. Home runs across the league are down to start the season, and a lot of that has to do with the weather early in 2018. All teams have had to deal with cold, wet conditions, and that kind of climate naturally suppresses fly balls. Once we get into June, July and August, expect to see balls fly out at a higher rate - another reason why using the 2017 standard deviation works well here - and the Yankees will be that much closer to the all-time record.

The other key is one Giancarlo Stanton. He hasn’t hit for the kind of power the Yankees would expect early, but we all know that’s going to change. Usually one player doesn’t have THAT great an effect on a team’s overall output, but a player like Stanton can hit 50 home runs without too much effort, so he’s the kind of outlier that could give the Yankees the edge they need to pass the 1997 Mariners.

The Yankees are on a roll, and for two weeks or so have been just about the most fun to watch that a ball team can be. A lot of that has to do with the team’s prodigious power, and it’s only going to get more and more fun the closer the team gets to 264.