How Big Is Too Big for Shortstop?

When examining the 2018 draft’s collection of top high-school shortstops, one is confronted with three vastly different physical entities in Santiago HS (CA) SS Brice Turang, Montverde Academy (FL) SS Nader De Sedas, and North Broward Prep (FL) infielder Xavier Edwards.

Edwards is explosive. A plus-plus runner with good hands and enough arm for the left side of the infield, he also possesses gap-to-gap power. He’s performed, in games, against elite pitching and might be my first pick among all 2018 high schoolers if we were picking teams for a game of sandlot ball tomorrow. He’s also a slight 5-foot-9 and 155 pounds.

De Sedas is a switch-hitting hammer who was being covered in his native Panama when he was just 13 years old. He moved to Florida late in adolescence and has shown big raw power from both sides of the plate, as well as feel to hit in games despite having adopted switch-hitting somewhat recently. But while De Sedas has premium arm strength and is smooth for his size, he’s also rather big. At a listed 6-foot-2, 192 pounds, De Sedas is already larger than Manny Machado (6-foot-3, 185) and Evan Longoria (6-foot-2, 170) were when coming out of high school.

Finally, there’s Turang. Lean, rangy, and acrobatic, he also features a plus arm. He’s instinctive, procedurally advanced, and a potential plus defender at short, but he may have limited, one-dimensional offensive impact.

As with any prospect, I’ve attempted to project the future defensive value of the three players mentioned here. Because of their vastly different builds, however, I became curious about the physical makeup of major-league baseball’s current shortstops and how the upcoming draft class — especially De Sedas, who belongs near the top of the class if he can stay at short — fits among them.

To address my curiosity, I began compiling not only the current heights and weights of the league’s shortstops but also their heights and weights at age 17 — or, roughly the age at which each of them was either drafted or signed out of Latin America. I then expanded my criteria to include all players who had recorded at least 450 innings at shortstop during the last three seasons. I also calculated both current BMI and also BMI at age 17 — as well as changes in height, weight, and BMI during that span.

There are some issues with this data. For one, it assumes that MLB teams are forthright about their players’ heights and weights, which is unlikely and, at times, demonstrably false. There was also no single source from which to obtain heights and weights for these players when they were 17. Where possible, I used draft data from MLB.com’s Draft Tracker, but I also dove into past Baseball America Prospect Handbooks, old AZL and GCL rosters, and even some local newspaper articles. (For instance, nothing was written about Wilmer Difo as an amateur and it took a 2014 James Wagner Washington Post article for me to find any record of his teenage weight.)

It was especially hard to find weights for Cuban players like Alexei Ramirez, as many of those players didn’t join MLB clubs until their mid-20s. If I couldn’t find old Cuban National Team rosters with the measurements of a given player at age 17, I got as close as I could. Alexei’s initial weight was measured at age 20, the furthest from 17 of any player on the list.

The entire table of data is located at the bottom of the article. Heights, which rarely changed from age 17 to present, are listed in inches. Here are the averages for current big-league shortstops.

Shortstop requires terrific lateral range. Modern defensive positioning might hide some deficiencies in this area — and this one specific skill has probably become less important than it once was — but it’s still a requirement. Statcast’s Sprint Speed Leaderboard, for example, indicates that shortstops run better than most other big leaguers, supporting the notion that players must exhibit a baseline level of athleticism for the position.

It’s intuitive that, as players get bigger and heavier, they become slower — and also less likely to remain at shortstop, where lateral quickness matters. I’m actually unable to find any statistical evidence that illustrates the effect of size on defensive performance — not within this sample of shortstops, at least. It’s quite possibly a product of the large sample sizes required for defensive metrics to become reliable, but I found no strong correlation between weight or BMI and any of Defensive Runs Saved, Range Runs, or Defensive Runs Above Average. But I think we can look at the shape of the data and see where the upper bound of physical viability lies. Corey Seager and Carlos Correa are our two tallest shortstops, responsible for the right-most bar on this histogram:

Meanwhile, here are the weights of all current shortstops:

And the BMIs:

The larger BMI figures actually do seem to correlate with a drop-off in defensive performance. Many players with a BMI of 28 or more in our sample have either already moved off of shortstop, are late-career stopgaps, or have clear defensive warts to the naked eye.

By stacking some histograms, it’s possible to see how the weight and BMI of shortstops changes from their earliest days as a prospect to physical maturity. First, with weight:

And then BMI:

As I collected the data, it looked as though there were some differences between the way domestic and international amateurs had developed. Here are the results when I split the two groups:

On average, Latin American shortstop prospects acquire more mass between age 17 and maturity. Socioeconomic factors are likely responsible for that. Because it’s my desire, however, to project domestic, draft-eligible amateurs, I’ll be using the data from that subgroup of current MLB shortstop as my main resource. There was no correlation between height and weight change within shortstop, so I’ve blanketed the average across all of the 2018 draft class. The names you see below are all 2018 draft-eligible high schoolers whom I’ve seen play shortstop. They’re sorted by projected weight (Prj Weight).

The bottom four names on the table are all players whom I’d already projected at shortstop based solely on my in-person evaluations from this summer. You can see De Sedas’ projected weight is right on the fringe of what we currently see at shortstop. Nine current/recent MLB shortstops weigh 215 pounds or more and most of them aren’t currently good defenders there. Corey Seager and Carlos Correa, each very rare talents, feature two of the better gloves in that group. Shortstops can compensate for a lack of range with other attributes (Correa, for example, features excellent arm strength) and it’s possible that De Sedas can do this (he has at least a 60 arm). I think his bat is impressive enough that he’ll garner top-10 consideration in next year’s draft even if he’s evaluated as a third baseman. But for now I think there’s reason to be apprehensive about projecting him as a shortstop. Turang, meanwhile, falls smack into the middle of the group, further supporting the notion that he’s a near lock to stay at short.

I also ran projections for prospects in pro ball based on their age-17 weight. The following table includes prospects who have garnered recent consideration at shortstop. Their projected weights are based on their weight at age 17. I’ve also included their means of acquisition in each case. Only Willy Adames has outgrown projection in a meaningful way.

And here’s the full table of data I compiled for major leaguers.