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Xavier Isaac's fantasy baseball prospect outlook, sleeper potential for dynasty leagues. Matt uses his custom suite of fundamentals-rooted evaluation tools.
Es,Tampa Bay Rays first base prospect Xavier Isaac is next up in a series in which I examine the evolution of the pro offensive fundamentals of 2022 MLB Draft signees from the high school class.
When I saw and filmed him in the Florida Complex League just after the Draft, Isaac showed good grasp of the strike zone and aptitude for covering the entire width of the plate. But he was not yet generating much in the way of louder contact.
In a 2022 Florida Complex League game, Isaac shoots an away pitch down the third baseline and into left field for a 2-run double
How should the professional plate profiles and offensive outcomes posted to date impact future forecasts of Isaac in real-world and fantasy baseball circles?
Prospect Analysis: Xavier Isaac
Evolution of Pro Plate Profile
An ever free-thinking Rays surprised many by committing the 29th overall pick of the 2022 MLB Draft and a full-slot $2.55 million bonus to the lefthanded-batting North Carolina prep first baseman, who many sites had outside the Top 100 draft eligibles.
The subsequent 2022 pro debut comprised 40 plate appearances in the Rookie-level Florida Complex League. 90 BB+HBP and 84 K Avoid Ratings were impressive for a not-so-well-known recent high school player facing a pitcher mix biased to that draft class' collegians and international free agent signees from prior annual classes.
A batted ball profile that produced few hits (8 AVG) but some extra bases (27 ISO) featured a heavier dose of LD but too few Pull OFFB and too many Pull GB.
In a 457 PA 2023 season spent more back in Low-A than late in High-A, Isaac seemed to trade some BB+HBP and K Avoid for contact that was louder and more aerial-biased relative to the 2022 debut.
An impressive pair of 87 AVG and 95 ISO Ratings on Batted Balls had been achieved more by pulling OFFB and avoiding Pull GB than by hitting LD.
Isaac began 2024 with 302 plate trips back in High-A. BB+HBP held steadier versus the brief 2023 High-A debut, but K Avoid plummeted to 23 from 80 before. Batted Ball Profile topped plus (87) thanks mostly to an outstanding 85 LD/98 IFFB Avoid/67 Pull GB Avoid hit trio that fueled a 100 AVG Rating.
Isaac was plenty strong enough and had the barrel sense, backspin, etc. then to generate 98 ISO despite very seldom pull-thirding a larger frequency of outfield flies (33 Pull OFFB << 81 OFFB).
From the standpoint that he had just posted a 23 K Avoid Rating while in High-A and was unlikely to have gone on a lengthier strikeout avoidance spree near the end of that stay, the zero K Avoid in Double-A was unsurprising.
The big bat continued to produce AVG and ISO on batted balls in the upper 90th percentiles at the final stop even while the batted ball profile skewed short on LD, Pull OFFB, and Pull GB Avoid.
Over a bonus 67 Arizona Fall League plate trips, K Avoid again zeroed out. But LD, Pull OFFB, and Pull GB Avoid favorably rose to propel Batted Ball Profile to 99 and fuel 99 AVG and 100 ISO on Batted Balls.
Isaac logged twelve 2025 MLB spring plate trips with a line disproportionately comprised of very low, often single-digit marks.
Isaac began to produce hits and extra bases at a high clip as the 2023 Low-A opener to his first full season played out and has consistently ranked among the best MiLB producers of hits and extra bases since graduating that level.
But strikeout avoidance abruptly became a big problem during the 2024 return to High-A and has since snowballed into a major one in Double-A and Arizona Fall League play.
Evolution of Pro Offensive Running
The 6-foot-3-inch, 240-pound slugger was surprisingly rated as an above-average offensive runner in all three pro seasons before posting a circuit-average 50 at Offensive Running in the 2024 Arizona Fall League. While he rates somewhat slow as a batter, all single-stop As Baserunner Ratings are half plus (70, at the minimum) or higher, with the exception of the 50 plays evaluated from 2023 High-A games.
Contrary to what a stationary physical-stature-based eyeball test would suggest, Isaac runs the bases quite well when teammates occupy the batter's box.
Dynasty Fantasy Baseball Focus
Over three pro campaigns, Isaac dramatically flipped from a hard-to-whiff recent prep with a quieter bat to an easy-to-whiff Double-A batter who packed one of the loudest bats in the minors.
Rays are generally considered among the smartest organizations, but the choice to move Isaac up from High-A to Double-A during 2024 skews dubious. Organizations go out of their way not to demote top prospects, but such should be considered as one route by which Isaac may be able to cut down strikeouts while also tinkering with some swing adjustments.
Projections at present would skew in the direction of a three-true-outcomes player who tallies almost exclusively strikeouts, walks, and loud, somewhat aerial-biased batted balls that produce at least extra bases at a more prolific rate if not also hits in general.
But the strikeout frequencies were so extreme in Double-A and next in the Arizona Fall League (and now again in a 2025 return to Double-A?) that it seems a stretch to even project Isaac as a major league semiregular. That is even truer when one imagines the future AAA strikeout percentage increasing even more as he cuts his MLB teeth for the first or maybe even the second to third time.
The big-bodied Isaac possesses sneaky good offensive running ability per the model deployed here, but that prowess is largely limited to when he is on the bases with others at the plate. During his earliest seasons, he might register as a half plus baserunner relative to much older MLB peers.
He will not tally too many stolen bases relative to players in general, but he just might by first baseman to designated hitter standards beyond adding baserunning value on other types of play events.
First base play was rough to begin his minor league career, but he has gradually improved to the point of being reasonably good during 2024. He even got two starts at right field in 2024 Double-A and five more in Arizona, though he was charged with two errors in the desert.
Today, the dynasty fantasy owner should stash Isaac as a powerful-batted walker with major whiff issues that must be monitored more closely over the next year plus.
Brief Explanation of the FaBIO Model
My Fielding- and Ballpark-Independent Outcomes (FaBIO) evaluation model sorts every plate appearance into one of 12 outcome bins (BB+HBP, K, IFFB, Pull-Third OFFB, Center-Third OFFB, Oppo-Third OFFB, Pull-Third LD, Center-Third LD, Oppo-Third LD, Pull-Third GB, Center-Third GB, Oppo-Third GB) and charges the pitcher and batter with their league's mean runs value for said particular event that season.
Dividing a batter's total number of expected runs by plate appearance (PA) yields expected runs per PA that can be percentile ranked relative to the league mean and standard deviation for that parameter amongst league batter qualifiers to arrive at their Overall Rating.
Its three subcomponents of BB+HBP Rating (based on BB+HBP per PA), Strikeout Avoid Rating (K Avoid, based on K per PA), and Batted Ball Profile Rating (expected runs per batted ball) are also reported to identify the path the batter traveled to reach their Overall Rating.
Overall Rating and Batted Ball Profile Rating of batters should be considered power- and speed-neutralized metrics since the real-world runs value of a single batter's typical OFFB or LD varies with their strength, and the expected runs value of their typical GB varies with their speed.
To better understand the Path to Batted Ball Profile, we will also examine percentile ratings for select batted ball event types (on a per-batted ball basis). To check how well expected batted ball outcomes match real-world ones, we will compute percentile ratings for hits (AVG) and isolated power (ISO, or simply extra bases) on batted balls (recognizing full well that these two parameters are neither fielding- nor ballpark-independent outcomes).
What most explains a batter's ability to generate hits (AVG) on batted balls is any LD, IFFB avoidance, Pull-Third OFFB, and Pull-Third GB avoidance. What most explains their ability to generate extra bases (ISO) on batted balls is any OFFB, Pull-Third OFFB, Pull-Third LD, and IFFB avoidance.
A percentile rating of 97 amounts to plus-plus (two standard deviations above the mean), 84 is plus (one standard deviation above the mean), 69 is half plus, 50 is average, 31 is half minus, 16 is minus, and three is minus-minus.
A new addition to this suite of evaluation models is the Offensive Running Rating. This tool quantifies how each relevant inning's run expectancy was impacted by the player's action or inaction as either a batter or baserunner on very specific types of plays that are more likely to involve one or both of their speed or offensive running techniques, plus acumen.
The evaluated batter and baserunner events are summarized in the graphic.
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