Original art by @snarshall
Ahh, the weight of expectations.
When a generational player suddenly looks mortal, fans and media search for explanations. This season, the Dodgers’ player raising the most eyebrows is Marcus Lynn Betts, “Mookie” to… well, everyone.
The eight‑time All‑Star and former American League MVP has hit poorly all summer, and his slash line (.238/.309/.370 through July 25) stands more than 170 points below his 2023 peak. Pundits have pointed to his transition from right field to shortstop and his age‐32 season as possible culprits. Yet those surface factors distract from what I believe is the most likely cause: at the end of spring training Betts suffered a mystery illness that caused him to lose 15-25 pounds in roughly three weeks.
To understand Betts’ season one must understand how severe weight loss impacts athletic performance, how Betts has compensated through defensive excellence, and why his performance this season, though mediocre by Betts’ standards, further cements his Hall of Fame credentials rather than damages them.
Athletes need muscles. Also, water is wet.
Standard medical guidance suggests that unexplained weight loss of more than 5% of one’s body weight, or more than 10 pounds over 6-12 months, is concerning and a red flag for more severe illness. These thresholds are important because the body’s energy stores and muscle mass are designed to support daily metabolic demand. Rapid weight loss signals that something has gone wrong with nutrient intake, metabolism, or both.
In March 2025, just as the season was getting started, Betts got sick and blew through those clinical red flags. At the beginning of spring training he weighed approximately 175 pounds. Late in March he told reporters that an undiagnosed stomach ailment left him “vomiting for two weeks,” unable to keep solid food down. The sickness caused him to drop somewhere between 15 and 25 pounds in about 3 weeks. Remember, 5% weight loss in 6 months is concerning; Betts lost 14% in less than a month.
That would be like Will Smith, at 195 pounds, dropping down to 168. Guys like Betts, at 5’ 10”, 175 pounds and able to dunk a basketball, are lean to begin with. Unlike us desk jockeys, they fight to keep weight on, typically taking in 3,500 or more calories daily to keep up with the physical demands of their profession. But Betts’ body revolted against him. At the time, he described the sensation bluntly to reporters: “My body is basically eating itself…every time I eat anything I vomit.”
In hitting, weight matters.
Baseball is a skill sport, but it is also bio-mechanical. Generating bat speed and hard contact requires leverage and coordinated rotation of the legs, core and upper body. A drop in body mass means a loss of muscle, which in turn reduces bat speed, but also the body’s ability to absorb the stresses of daily play. Less muscle means less stored energy in the form of glycogen, the body’s internal blood sugar bank. Less glycogen means quicker fatigue and reduced peak force output. For hitters like Betts who rely on quick hands and a compact, powerful swing, even modest decreases in body mass can translate into slower bat speed and weaker contact.
Statcast data from MLB’s Baseball Savant backs me on this. Before the illness, Betts routinely ranked in the top quartile of hitters in average exit velocity and bat speed. SI reported that in 2025 his average exit velocity fell to 88.3 mph, down 4.1 mph from his 2023 peak and the lowest of his career. His bat speed dipped to 68.8 mph, ranking only in the 11th percentile of MLB (although, Betts’ bat speed has never been great). Betts’ barrel rate (the percentage of batted balls struck with ideal launch angle and exit velocity) dropped to 5.5 percent, and his hard‑hit rate plummeted to 34.1 percent.
Can you blame the guy? He just lost 25 pounds three months ago. In retrospect, this was predictable. Of course his bat speed and power numbers were going to suffer.
Q: But what about his age, or changing positions to shortstop?
A: Get his HOF plaque ready.
Look. 32 is not old by today’s baseball standards. Many elite hitters – and although his numbers are suffering this year, Betts is still an elite hitter – maintain high offensive production into their mid‑30s. Derek Jeter hit .330 at age 32 and remained above league average until 37. Betts’ body type and skill set (athleticism, plate discipline, contact ability) typically age better than sluggers who rely on brute strength. The rapidness of his drop from a .307/.408/.579 line in 2023 to .238/.309/.370 in 2025 suggests an external shock rather than a gradual decline. And his plate discipline remains excellent: his 2025 strikeout rate is hovering around 11%, elite for a modern hitter. Walk rate has dipped only slightly from 10.7% to about 9%. The elite mechanics are intact.
So much has been made of the move to shortstop. SI speculated that “…the physical toll of playing short every day could be contributing to his struggles at the plate.” There is merit to the idea that moving to the infield from outfield adds wear and tear. However Betts’s hitting while playing short last year was solid, even though he was re-learning the position in real time. And re-learned the position he has. While his bat has struggled, Betts has become an above average, maybe excellent, shortstop.
According to Baseball‑Reference’s fielding metrics, Betts ranks second among MLB shortstops in total zone runs with 9 runs saved as of July 25th. Outs Above Average (OAA), a more advanced measure provided by Statcast, placed him in the 76th percentile, well above average. His throwing accuracy has visibly improved from a year ago. Baseball’s internal tracking labeled his range (as measured by Range Factor per nine innings) as 4.47, above league average.
Only a handful of stars – most notably Robin Yount in the 80’s – have played both the outfield and shortstop successfully, though Yount started as a shortstop and moved the the outfield, the “easier” direction. Betts has joined a very exclusive club and in doing so has built on his HOF resume.
Hall of Fame voters also consider excellence over a sustained period. Betts’ eight All‑Star selections, seven Silver Slugger Awards, six Gold Gloves, three world championships and 2018 MVP provide a resumé few can match. Even in 2025, while his bat has suffered, he’s remained a team leader, has shown up every day with a smile, talks to fans and the media. He’s Mookie.
When he eventually enters Cooperstown, the plaque will list his MVP award and his rings. It should also commemorate the season he lost 14% of his body weight, learned to play shortstop, and still found ways to help his team win.
If the Dodgers win the last game of the season again this year, Betts will be a first ballot inductee. He should be, regardless.
In a sport obsessed with numbers, context matters.
Sources
https://www.mlb.com/news/mookie-betts-battling-undiagnosed-illness
https://my.clevelandclinic.org/health/symptoms/unexplained-weight-loss
https://www.uclahealth.org/news/article/unexplained-weight-loss-what-it-could-mean#
https://www.espn.com/mlb/story/_/id/44385494/dodgers-mookie-betts-dealing-illness-lost-15-lbs
https://people.com/dodgers-star-mookie-betts-lost-25-lbs-from-mystery-illness-11702538
https://www.si.com/mlb/mookie-betts-decline-inside-the-numbers#
https://www.baseball-reference.com/leagues/majors/2025-fielding-leaders.shtml#
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