Prospect Report: Red Sox 2023 Imminent Big Leaguers

The top-ranked prospect in the 2021 draft, Mayer dropped to fourth overall, where the Red Sox were happy to scoop him up and sign him for a higher dollar amount than first overall pick Henry Davis. In his first full season, Mayer slashed .280/.399/.489, hit 30 doubles and 13 homers, and was 17-for-17 on stolen base attempts as he continued the track record of premium offensive performance that he’s displayed since he was a high school underclassman. He has a big, prototypical frame, a mature approach, and a left-handed stroke so gorgeous that it’s rumored to be dating Pete Davidson. Mayer’s underlying TrackMan data is only okay, and he’s hovering at or below the big league average in most chase and contact rate categories, though he’s also generating impressive power for a shortstop his age. His front side is fairly stiff through contact, which may impact his ability to scoop lower pitches in the future, an issue that Jarred Kelenic and Spencer Torkelson only had exposed once they reached the big leagues. As far as defensive projection is concerned, a boxy frame, medium straight line speed, and an awkward running gait push and pull against Mayer’s excellent defensive instincts, first-step quickness, and strong arm. He was already noticeably thicker in 2022 than he was in high school, though he looked very svelte when he reported for 2023 Spring Training. Just through sheer size, it’s possible he will move off of shortstop eventually, but it probably won’t be for a while; the longer he stays there, the more margin for error his hit tool will have as he begins his big league career. Apprehension around the contact piece of the puzzle here is all that keeps him from the 60 FV tier at this stage. It’s important to acknowledge the risk of his profile at this stage, but Mayer still projects as an extra-base machine at shortstop and an impact big leaguer.

Bleis signed for $1.5 million out of the Dominican Republic in January of 2021, and after a solid showing in the DSL that year, he created huge buzz on the complex in Fort Myers throughout 2022 because of his bat speed and power. This is one of the toolsiest prospects in all the minors and one of the players on the overall Top 100 who has a chance to “Chourio,” i.e. leap into the top-10 mix within the next year.

Bleis has all-world bat speed and rare rotational athleticism. His swing is a little odd and upright, and his hands load with a bit of a hitch, but he is still able to guide the barrel around the zone and produce shocking raw power for such a lithe teenage hitter. Though he’s of relatively narrow build, he still oozes projection, and his present footspeed gives him room to fill out and slow down some while remaining in center field. Even though his career walk rates are extremely low (7%) for a complex-level prospect (where pitchers often struggle to throw strikes), Bleis’ chase rates in 2022 were closer to average. Whether he adjusts to more cautious and competent pitching as he moves through the minors, we just won’t know until it happens — he was chase-prone in 2023 Grapefruit League play — but the more granular statistical indicators here (what Bleis’ underlying contact and chase rates are relative to his strikeout and walk performance) suggest he’s going to improve in these areas. Even if you dismiss that, the measurable power that’s already here is incredible and reinforces the visual evaluation of Bleis’ electric talent. His rate of hard, impact contact is near the top of the scouting scale when you adjust for age and is already comfortably plus relative to the big league rates in some areas (like barrel rate). When you bounce his skill set off of those of recent top high school prospects, Bleis’ compares favorably. If you dropped him into the 2022 draft class (with high schoolers his age), he’s going in the top five picks.

Casas spent most of 2022 with Triple-A Worcester and hit .273/.382/.481 there amid a two-month absence due to a high ankle sprain. He debuted with Boston late in the season and flashed the titanic power that promises to make him a valuable big league regular, and also ran the high walk and strikeout rates that readers should expect from him going forward. He went to the Dominican Winter League to be part of Licey’s prospect-studded lineup (Elly De La Cruz, Ronny Mauricio, and a few others were also on that roster at the start of the LIDOM season), but a knee injury ended that jaunt after just three games. While manager Alex Cora has indicated that they’ll spell Casas versus the occasional lefty starter, he entered the spring poised to break camp with the big league team and put together a hot Grapefruit League performance.

A career .269/.374/.485 hitter in the minors, some front office analyst sources who provided feedback on the Top 100 list are skeptical Casas will make enough contact to profile comfortably as an above-average regular at first base. He struggles with softer stuff in the bottom of the strike zone, and his in-zone and overall contact rates in 2022 were 78% and 70% respectively, similar to Nolan Gorman, Franchy Cordero, Bobby Dalbec and others who have tantalizing power but have sometimes been frustrating big league hitters. But in Casas’ case, there is *so much* power here that he profiles as an above-average big league run producer at first base. Injuries and the pandemic have limited him to just 284 career minor league games since he was drafted in 2018, and his bat-to-ball skill has projection deep into his mid-20s as he continues to gain actual pro experience. The amount of power here is sensational: Casas is capable of hitting huge tanks to all parts of the ballpark, and his hard-hit rate in 2022 was a whopping 50%, which would have been top 15 among qualified big league hitters. A lumbering, heavy-bodied athlete, his injury track record is also a bit of a concern. Part of Boston’s motivation to DH him sometimes and caddy for him with righty-hitting corner bats against some lefty starters is to manage his workload with this in mind. This combined with the undercooked hit tool might lead to some big league growing pains and medium production at first, but over time, Casas should become a middle-of-the-order force capable of hitting 35-plus annual homers.

Rafaela had a breakout 2022 season, hitting .299/.342/.539 mostly at Double-A Portland. And even though he has some approach-driven bust risk (he swings at just about everything), he does enough other stuff to project in a prominent big league role if his chase proves too much for him to be an everyday player. For one, he’s a Gold Glove-caliber center field defender, capable of making tough plays look easy and impossible plays possible, especially around the wall. That’s mind blowing when you consider that Rafaela has only been playing the outfield for two years. Here he’s projected to continue to improve on defense as he gets more experience, which would make him perhaps the best defensive center fielder in baseball at peak. Rafaela is also capable of playing a couple of spots on the infield, though not nearly as well; unless his approach is actually a problem and shifts him into a premium utility role, he’s probably just going to play center field all the time.

Rafaela’s stance is Mookie Betts-like, his swing rhythmic and athletic, though he doesn’t take very discerning at-bats, chasing at a whopping 40% clip in 2022. Despite that extreme amount of chase, he only struck out at a 21% rate and also doubled his previous career high in homers with 21. Most of Rafaela’s underlying contact rates and measurable power data is middling, and his peak exit velos aren’t what you’d typically expect from a 20-homer threat, except he does seem to hit the ball fairly hard and in the air frequently relative to his peak exits. There might be more game power here than there is raw power, or at least more game power than you’d expect from someone who has some approach-related red flags. There’s still risk that Rafaela walks the Cristian Pache path, as his issues are similar to the ones that have apparently undone the young A’s outfielder. More likely is that he’s akin to Kevin Pillar, and there are scouts who think Rafaela’s frame will continue to add strength such that he hits for more power than Pillar was able to.

Yorke was the biggest surprise of the 2020 draft’s first round. He was a known bat-first prospect from California, but time off recovering from a shoulder surgery and the pandemic made him tough to evaluate properly before the draft — tough enough that he was not generally seen as a first-round prospect. His 2021 pro debut was a rousing success, as he hit .325/.412/.516 across two A-ball levels as a teenager. In contrast, his 2022 was a tough-luck grind, as he hit just .232 at Greenville and dealt with myriad injuries, including turf toe, back stiffness, and wrist soreness that reared its ugly, uh, wrist during the regular season and again when he went to Arizona to pick up reps in the Fall League. Yorke’s rhythm and timing at the plate were fantastic in the desert, though, and I’m inclined to dismiss his 2022 as being the result of his injuries rather than a real regression in skill or exposure of a flaw in his offense. Yorke and his French swing (because it is evocative of Ty France) looked like a high-probability big league hitter with a well-rounded contact and power combination in Arizona, enough to project as a regular if he can stay on the dirt. If there’s a real long-term concern, it’s that he seems injury prone and has now had several disruptive maladies during the last couple of years.

When Yoshida first appeared on The Board a couple of years ago, he was evaluated in a way that pegged him as a fun part-time weapon (I compared him to Lenny Harris) rather than the $100 million player the Red Sox believe him to be. Boston signed Yoshida to a five-year, $90 million contract and paid an additional $15.4 million posting fee to the Orix Buffaloes — the kind of deal you give to a 2-WAR player, a hitter who exists in the middle third of MLB’s corner outfield talent hierarchy. Is it possible that the little Yoshida — all 5-foot-8, 176 pounds of him — can thump with that contingent? In his own way, yes. While Yoshida’s skill set is shaped in an extreme hit-over-power style atypical of a big league corner outfielder, there are others who have had success with similarly tailored talent, most especially Steven Kwan and Jeff McNeil, with the likes of Tony Kemp and Jurickson Profar providing a look at the bottom of what an acceptable range of performance outcomes for Yoshida would be.

This guy can hit. Yoshida is a career .327/.421/.539 hitter in NPB with more walks than strikeouts; the last two seasons, he’s actually walked twice as often as he’s struck out. He was almost impossible to strike out in Japan, and his feel for contact is superlative enough that even though he’s not very physical and is a left field-only guy, he’s arguably elite at the game’s most important skill. His ability to maneuver the barrel around the zone by altering not only his hands but also the overall posture of his body is very special, and there isn’t a spot in the strike zone where he can’t make contact with the baseball. He can drop the bat head to golf out middle-in mistakes and get extended on fastballs up and away from him to do doubles damage the opposite way. But while Yoshida is such an explosive rotator for his size that his bat often strikes the ground behind him at the end of his follow through, he hits the ball on the ground a lot, with a GB% in the 47–51% range for the last six seasons. Opposing pitchers can limit his ability to do damage by working him with soft stuff down and away, though Yoshida is still going to find a way to put the ball in play. His measly 5% swinging-strike rate was seventh-best among qualified NPB hitters in 2022, and only one of the hitters ahead of him could muster more than three homers; Yoshida yanked out 21. Among the best contact hitters in NPB, he separated himself with how much power he got to.

Will some version of this hold up against MLB pitching? When you isolate Yoshida’s performance against hard fastballs, you start to get a better idea of how things might look over here. Versus fastballs 93 mph and above (202 pitches), he hit .273/.333/.455; against 94 mph and up (153 pitches), he hit .279/.340/.395; and against 95 mph (88 pitches) and above, his line was .296/.345/.370 (all of this is from Synergy Sports). Anything more than that and the sample gets too small to be meaningful, and it’s possible 88 pitches already is. You can see the dip in his SLG within that sample, but the good news is that Yoshida maintains about a 5-to-1 ball-in-play-to-whiff ratio within all three of those velo bands. The hit tool is going to translate, and his plate discipline probably will, too; his 23% O-Swing% would put him among the majors’ 10 most selective outfielders. The contact/OBP combo should enable him to produce in the 1.5–2 WAR range, similar to the last couple seasons of Andrew Benintendi or a more patient Alex Verdugo. It’s possible that the amount and quality of contact Yoshida makes gives him a higher power ceiling than I anticipate.

Had Walter been healthy for all of 2022, he probably would have been on the Top 100 list entering the year as a plug-and-play mid-rotation starter. When he was healthy last season, his average fastball velocity (90 mph) was down three ticks from the prior year (93), and he missed the back half of the summer due to a bulging disc in his back. He entered 2023 on the outside of the big league rotation looking in, and even after a few spring injuries to other members of the roster, he was optioned after just three Grapefruit League outings, all out of the bullpen. The former Blue Hen has plus command of three pitches, and whether or not his velocity returned was the key variable to watch early in 2023. He peaked at 93 and averaged 91–92 before he was optioned, a step in the right direction but not all the way back to peak form.

Walter’s low slot is a non-traditional look for a starter, but unless injuries push him to the bullpen, his command and repertoire depth give him a starter’s toolkit. The sink and tail created by his low, slingin’ arm slot keep his fastball off barrels, and the shallow angle his delivery naturally creates gives him the option to run his fastball up the ladder for some whiffs, but he’s better equipped to do that if his best velocity comes back. Because his low slot gives righties a long look at his fastball, Walter throws a lot of changeups to them. That pitch played like a premium weapon in 2022 (it garnered a 50% chase rate!), and his feel for locating it to his arm side is robotically consistent. His sweeping low-80s slider also played like a plus pitch (59% whiff rate) and, as you can probably imagine since we’re talking about a low-slot guy, is especially tough on lefties. Most incredibly, Walter’s strike-throwing ability with each pitch gives him a shot to have 70-grade command. He threw strikes with his fastball and changeup at a 75% and 72% clip, respectively, and his slider for strikes “merely” 64% of the time. To recap: this is a near-ready lefty with plus-plus command of two plus secondary pitches and a fastball that has multi-faceted utility despite below-average velocity. It’s possible righty big league hitters will tee off on the fastball if Walter is destined to live in the 90–92 mph range, but here he projects as a no. 4/5 starter during the regular season who shifts into a valuable long relief role on the postseason roster. The chance that his velocity returns is where the + in his FV comes from here.

Valdez has been among the more divisive prospects here at FanGraphs during his time on the radar, at times evaluated as a positionless prospect with a relevant hole in the top of his swing, and others as a versatile, well-rounded lefty stick likely to play an integral part-time role. His 2022 season, in which he hit .296/.376/.542 and tallied 60 extra-base hits against upper-level pitching, solidified him as the latter, and he was part of the two-player package that came back from Houston for Christian Vázquez.

Valdez packs quite a wallop for a 5-foot-9 hitter. He swings really hard and is capable of hitting for power to all fields, turning on pitches that find the inner third of the plate and bending to spray hard contact the other way against stuff finishing away from him. His hands are a little noisy as they load, and he has a bit of a hitch before they fire, but his levers are so short that he tends to be on time anyway. His stance and aggressive, uphill swing are like a cover band’s rendition of Juan Soto’s cut. Vulnerable to fastballs running up and away from him (even ones that finish in the zone), Valdez’s hit tool will likely settle in south of average, but he’s going to get to considerable power thanks to his bat speed and damage-seeking style of swinging. He has experience in both outfield corners and at every infield position but shortstop, most frequently second base. Like a dull Swiss Army knife, he isn’t especially good at any of them. He’ll make some sweet plays out of sheer effort but struggles at other times due to below-average range, hands, and actions, frequently costing the team an out on double play attempts due to a slow pivot (his feeds to the bag tend to be good, though). The death of the shift will further stretch him on defense, and he might end up playing more 1B/LF than anywhere else over time, but there’s enough platoon-friendly offense happening here to consider Valdez a core part-time player.

The pandemic and an early 2021 Tommy John surgery cost Mata two consecutive seasons. When he returned in 2022, he had transformed both his body (which is now quite lean) and his repertoire (which is now five pitches thick). He now makes even use of both four- and two-seam fastballs that average 97 mph, up three ticks from the last time he pitched for a whole season. He has an upper-80s slider (his most-used pitch if you consider each of his fastballs to be their own offering), a low-80s curveball and a 88–91-mph changeup, all of which flash above average. But while it looked like Mata had turned a corner from a strike-throwing standpoint in 2019, he was back to his walk-prone ways in ’22, though that might be more to do with him shaking off two years of rust rather than his actual level of ability.

If, another year removed from TJ, he can throw more strikes with a pitch other than his slider (which he commands better than the rest), then he’ll cleanly project as a hard-throwing sinker/slider no. 4/5 starter. If not (and Mata’s lack of option years relative to other Red Sox 40-man occupants plays into this, as well), then he’ll still be a really nasty bullpen weapon who can come in with traffic on the bases, get you a ground ball, and then work the entire next frame or two because of his repertoire depth and starter background.

Murphy’s performance, from both a strikeout and walk standpoint, dipped after promotion to Triple-A in 2022, but he did enough during the season to solidify himself as a starting pitching prospect rather than a smaller, inefficient long reliever. He endured a 40-inning workload bump and was still holding low-90s velocity by the end of the year, and his heater plays up some because of its life and uphill angle. He popped a few 95–96-mph fastballs during his spring start against the Twins but was back in the low-90s during his next outing (is Minnesota’s TrackMan hot?). Lefties with changeups as good as Murphy’s tend to have long big league careers. He kills spin on his so well that it sometimes has splitter-like spin rates, and it features above-average action and movement. His 81–85-mph slider is not quite as nasty and played more like an average pitch in the minors, and his mid-70s curveball is often a get-me-over pitch if he needs to throw a strike with something other than his fastball. It’s back-of-the-rotation stuff with enough strikes to project in that role so long as Murphy continues to work with the efficiency he did for the first half of 2022. If not, he’s still going to be a good long reliever once his options run out.

A torn Achilles tendon in 2019 cost Hamilton his junior year at Texas; the injury also dropped him to the later part of his draft’s second day, where the Brewers selected him in the eighth round. He finally got his first taste of pro baseball in 2021, and a season defined by gaudy stolen base totals ended with him being traded to Boston in the Hunter Renfroe deal. In 2022, Hamilton’s first season in the Red Sox org, he slashed .251/.338/.402 at Double-A Portland (generating a pretty medium 104 wRC+) and stole 70 bases (!) in 78 attempts. Hamilton is a 70-grade runner who gets down the line in the 4.00–4.10 second range regularly. Minor league camera operators have trouble keeping him in frame, and his speed forces opposing infielders to rush their throws, often impacting their accuracy. This speed combined with Hamilton’s suitable shortstop defense make him very likely to play a part-time big league role. He has made plus rates of contact in the minors but has done so as an old-for-the-level player, so it feels prudent to round down on that tool at least a little bit. Vulnerable on the outer edge, Hamilton is best at turning on inside pitches, which is really the only part of the zone in which he’s able to hit for power. More “fine” than excellent at short, he doesn’t have the skillset of a premium utility man and is more of a niche player who can impact the game with his speed. If he continues to get reps in center field (he played two games there in 2022), then that premium utility role is in play.

The other component of the Christian Vázquez trade, Abreu is a stocky corner outfield prospect with deceptive speed for an athlete of his build. While he’s a stretch in center field (though he has played there some), he projects as a plus defender in a corner with a plus arm. He was one homer shy of having a 20/30 season in 2022 when you combine his Houston and Boston stats, and just a hundredth of a point from a .400 OBP on the year. While some of Abreu’s sky-high walk rate from 2022 feels faulty due to sheer passivity at the plate, the power component of his profile is real. He has above-average raw power, and his swing is geared for extreme lift, something his relatively short levers enable since his barrel needs to take a longer path to get on such an uphill plane. This style of hitting does leave Abreu vulnerable to high fastballs, which he often swings underneath. The flimsiness of the hit tool is what separates him from a plug-and-play corner platoon bat like Seth Smith or Matt Joyce, the 45 FV prototypes of that role. His tools are still solid enough for him to impact the game in a low-end version of that role, and if it turns out his plate discipline is actually as good as it appeared to be on the surface of his 2022 stats, then he belongs a tier above this.

Broadway has coasted through the minors in a (mostly) single-inning relief role, reaching Double-A Birmingham about a year after he was drafted by the White Sox, and was shortly thereafter traded to Boston as the PTBNL in the 2022 Jake Diekman deal. Broadway has a vertical fastball attack, sitting 93–95 with riding life and backspin thanks to his vertical arm slot and powerful drop-and-drive delivery. He hammers the zone with his fastball, and both of his breaking balls — a mid-80s slider and low-80s curveball — generate above-average whiff and chase. He’s a standard middle inning relief prospect with a very high floor because of his propensity to pound the zone.

Hernández was acquired as part of the trade that sent Jeffery Springs to Tampa Bay not long before the 2021 season, and since then he’s spun his wheels in the upper levels of the minors, struggling with the same issues that made him a maddening Rays prospect — namely, his propensity to chase. At Triple-A Worcester, he offered at a reckless 58% of pitches and posted a 41% chase rate (big league average is about 33%). There’s still plus pull power here; it’s just tough for Hernández to get to it in games because of how often he gets himself out. A fair receiver and ball-blocker with a plus arm, in many ways he is a less toolsy version of Jorge Alfaro, who is now ahead of him on the organizational depth chart. Still hellbent on taking the longview with power-hitting catchers due to industry-wide scarcity at this position, here Hernández continues to project as a bat-first backup catcher, but it’s probably time to stop waiting around for him to become disciplined enough to profile in an everyday capacity.

Kavadas had a monster draft spring at Notre Dame, with 50 walks and 22 home runs in 47 games helping him put together an eye-popping batting line of .302/.473/.767. There was some talk of him going as high as the second or third round, but a surprising tumble to Day Three ended in the 11th round, where he signed for a $250,000 bonus. Power is the calling card for Kavadas, who had some of the best exit velocities in his draft class — something that now extends to the minor leagues. He’s capable of majestic moonshots when he successfully pulls a fastball, which he combines with an exceptionally patient approach that crosses the line into passive at times. He has a frame more suitable for beer league softball and is a well below average runner and a fringe defender at first base who likely would be better off as a designated hitter (which he’s projected as here). The length of his swing makes it tough for him to get to fastballs up and away from him, and the need to commit to heaters early also leaves him vulnerable to breaking balls in the dirt. Kavadas likely won’t make enough contact to be a regular DH but, like Matt Stairs and Darick Hall, he’s going to be a dangerous bench weapon.

It’s been quite a ride for Kelly, who entered professional baseball as a undrafted free agent. He was released multiple times, dealt with elbow issues, and finally reached the big leagues in 2022 at age 27 thanks to much improved velocity. Kelly is a big, burly man with a big, burly fastball that sits in the mid-90s and touches 97–98 mph at times. He lacks any modicum of precise command and instead is just trying to get it over the plate to set up his ridiculous low-80s changeup, which is comfortably plus. Sourced pitch data shows Kelly’s breaking ball velocities have changed over time, from a mid-80s cutter-type thing to a slower, more slider-y look, so it’s possible he’s altered aspects of his breaking ball since joining the Sox and that this pitch might have some late-career growth. For now he’s a fastball/changeup reliever with well-below average command and is likely to play an up/down relief role.

Koss is a perfectly capable shortstop defender who has performed close to the league average at each minor league stop. He is not an especially toolsy offensive player and has a collection of 40- and 45-grade skills on that side of the ball which have enabled him to hit about 15 annual homers up through Double-A. It’s not enough for him to have a slam dunk, consistent big league role, but Koss does project as an above-replacement player who is likely to hop all over baseball, on and off 40-man rosters wherever his glove is needed.

Scott barely caught at Vanderbilt and as a draft prospect was considered either a light-hitting 1B/LF or a developmental project as a catcher. The Red Sox have taken the second line of play, and it just might work. Scott and his excellent plate discipline have now performed above the league average up through Double-A, and he has made real strides on defense, where he is now a fair receiver with a nearly average arm. Scott’s ball-blocking could still use some work, but he’s not far off from being a passable all-around catcher. His offensive skills are led by his plate discipline, which is among the best in the minors. He’s best at attacking pitches he can damage, but struggled with big velocity in a small 2022 sample. He’s tracking like the third catcher on a 40-man roster.