Don’t Forget About Brandon Marsh by Justin Choi February 21, 2022 Kiyoshi Mio-USA TODAY Sports Here’s a somewhat uncomfortable truth: The majority of rookies kind of stink. Everyone wants their team’s star prospects to take off as soon as they step foot onto a major league diamond, but the reality is that development takes time. Last season, for example, rookie hitters collectively put up a 87 wRC+, and looking at the past ten seasons, that figure has ranged from a low of 83 to a high of just 93. Not everyone hits the ground running. Enter Brandon Marsh. His first 260 big league plate appearances resulted in a 86 wRC+ — pretty much average for a rookie. That can be interpreted as either a good or bad sign. On one hand, he performed like the typical rookie, and his prospect pedigree suggests room for growth. On the other hand, that isn’t a guarantee, and an 86 wRC+ is an 86 wRC+, no matter the context. This ambiguity could be partially why he hasn’t been at the center of prospect discourse. It’s not as if he shined like Wander Franco, and it’s not as if he bombed like Jarred Kelenic, whom we’re inclined to give the benefit of the doubt. A so-so debut isn’t one people remember. But I’m here to argue that Marsh is one of the most interesting young hitters around, worthy of your utmost attention. And it all starts with a number one might consider a red flag: a .403 BABIP. Among hitters with 200 or more plate appearances last season, Marsh’s .403 BABIP ranked second. You probably know the stigmas surrounding the metric — that it can fluctuate wildly and is usually something players can’t control. But while BABIP for pitchers is notoriously noisy, hitters are more predictable. Those with fly-ball tendencies like Joey Gallo tend to run a low BABIP, as fly balls rarely land for hits. Those who don’t have as much loft like Adam Frazier fare better, but groundballs are also at the whims of batted ball luck and infield positioning. No, to maximize BABIP, one must become a line drive machine — like Brandon Marsh. Of Marsh’s 147 batted balls last season, 49 were line drives, for a rate of 33.3%. That was tied for the second-highest rate in baseball, and that’s with a low minimum of 100 batted balls. And that matters, because the league-wide BABIP on line drives was an astonishing .622, the highest of any batted-ball type. There’s nothing here in regards to sustainability, but the point is that Marsh’s approach is what granted him BABIP success. His swing is compact and direct to the ball, which is perfect for line drives. That sweet swing did him another favor. Just one of his batted balls was a popup, for a rate of 0.7% — and the league-wide BABIP on popups was an abysmal .017, the lowest of any batted-ball type. This isn’t brand-new territory; according to a January 2021 scouting report from Prospects Live, Marsh ran “one of the lowest infield fly ball rates” during his time in the upper minors. All in all, he has a track record of avoiding mis-hits. Now it’s time for the fun part. I went through the list of hitters with a minimum of 100 batted balls and calculated the Z-score (i.e. how well he fared relative to the sample mean) for each’s popup and line-drive rate. Here they are plotted below, with Marsh the point in red: Pretty neat, right? The scatterplot shows you that not only was Marsh one of the best hitters at maximizing his BABIP potential, but also that hitting ample line drives while avoiding popups is a difficult task. Most hitters are either (a) good at only one aspect, or (b) average-ish at both. There’s another component to BABIP that further differentiates Marsh, though. Even if a hitter makes poor contact, especially on the ground, there’s always the hope of winning the showdown at first. Doing so requires quick feet, and well, Brandon Marsh is one fast man. He didn’t get many opportunities to show off his wheels last season, but here he is his element, beating out a throw from Leury García: Baseball Savant pegs Marsh’s sprint speed as 29.1 feet per second, which places him roughly in the 95th percentile. Let’s fold that into another graph. I calculated composite Z-scores of popup and line drives, with the signs reversed so that hitters are given positive scores for fewer popups. Plotting them against Z-scores for sprint speed produces the following: This time, the additional coloring isn’t even necessary. Marsh is out on an island of his own. None of this is to say that Marsh will sustain a BABIP north of .400, but this wasn’t merely a stroke of luck; the skills are all there. And one thing that stood out to me while researching this piece is how all the projections systems seem to hold his limited debut in high regard. They do have minor league data to incorporate, but it’s amazing that his average BABIP projection for the 2022 season is .344. That raises the question: Given that he had a .403 BABIP across 70 games, what’s the likelihood that his true talent BABIP is .344? Let’s crack that nut, Thomas Bayes-style. Imagine we know absolutely nothing about Brandon Marsh’s talent as a baseball player — maybe just a few first impressions. Long levers. Nice beard! We do know, however, that it’s unlikely he’s a genuine .344 BABIP hitter — say, a 10% shot. Conversely, let’s assume there’s a 90% chance that his BABIP will match the league average; it was .293 last season, so we’ll roll with that. These are our “priors,” or the underlying statistical assumptions. As the season unfolds, though, it becomes clear that Marsh is no ordinary player. We now have that 70-game sample, so it’s time to update our assumptions. To do that, we need to find two conditional probabilities. The first is the probability that he records a .403 BABIP given that his true talent BABIP is .344. The cool thing about baseball is how well it’s suited to a binomial framework. Think about it: Each ball put into play is an independent trial resulting in either a hit or an out; in a way, a .344 BABIP represents a 34.4% chance that a ball in play winds up a hit. Therefore, we can simply plug Marsh’s numbers into a binomial calculator. The second is the probability that Marsh records a .403 BABIP given that his true talent BABIP is .293, which is also made easy by the calculator. I’m not going to agonize you with any additional math, but basically, all this works out to… 66%! There’s a strong likelihood that Marsh’s true talent BABIP really is .344, and that a relatively small sample can tell us lots about an individual. (A few caveats: Those priors from earlier are incredibly simplistic. What actual projection systems do is establish a wide range of possible outcomes, but that wasn’t feasible for the sake of one article. In addition, we need to remember that Marsh’s debut is the sole basis of this optimistic outlook. If his BABIP plummets this season, our updated probability will reflect a new reality in which he isn’t as special as once thought. As always, future performance remains unpredictable.) On that note, it’d be remiss to ignore the elephant in the batter’s box. What’s the biggest reason why Marsh hasn’t taken off? Here’s a somber statistic: He struck out in 91 of his 260 trips to the plate, for a rate of 35%. The whiffs have been there in the minors, and they couldn’t have been any more apparent in the majors. It evokes the small but real possibility that he doesn’t make enough contact to become a big league regular. His ceiling, for now, is capped by this unwanted abundance. But if there’s reason to be hopeful, it’s that rookies in general rack up a ton of whiffs: 26.6% of the time, compared to the league average of 22.6% last season. Major league pitching is getting nastier, and unless you’re a once-in-a-generation talent, adjusting to better stuff takes time. So it’s unlikely Marsh’s strikeout rate will continue to climb. In fact, it’s more likely that it goes downhill from here. Besides, he might not need to trim too much off his strikeout rate to become a viable contributor. The role model is Chris Taylor, who despite the whiffs has hit line drive after line drive en route to a 116 wRC+ with the Dodgers. So when major league baseball comes back to life, I recommend paying close attention to Brandon Marsh. He may not have the flashiest tools or the most renown, but what he accomplished last season contains the ingredients to a successful career. All that’s left is putting them together.