Three arms with a plus fastball
These three arms have some nice traits on their fastballs.
Justin Slaten
The Red Sox traded for Justin Slaten from the Mets after New York selected him in the Rule 5 Draft, which Craig Breslow said in the post-Rule 5 press conference that it was a previously worked-out deal if the Mets took Slaten. With him being a Rule 5 pick obviously, Slaten will need to be on the major-league roster for the entirety of the season if the Red Sox choose to keep him.
Texas has a pretty stacked roster given that they just won the World Series, but some were a bit surprised that the Rangers still didn’t protect Slaten. It’s an impressive arm with a big-league arsenal that had noticeable success at Double-A in ’23 before being called up to Triple-A at the end of the season. Despite him only having limited innings at the Triple-A level and him having mostly unsuccessful seasons before 2023, his stuff should allow him to succeed in the majors — he has to spend the entirety of the season on the 26-man roster if the Red Sox want to keep him for good.
At 6-foot-4, Slaten’s high release point gives the fastball a VAA above -5° but it still averages above 96 and nears triple digits with 18" of ride. Has plenty of life and plays well up in the zone with above-average spin, and it’s able to get decent whiff rates despite the less-than-ideal approach angle. The right-hander throws it for strikes with strong in-zone rates and it grades out well by models.
Slaten’s most common secondary pitch is his cutter which sits 88–90 and has some horizontal movement to it, which he pairs with a low-80s slider that’s thrown less often but still prevalent — gets above 10" of sweep and shows an ability to garner chases and miss bats. Baseball America gives it an impressive 127 Stuff+ and he was featured on BA multiple times leading up to the Rule 5 Draft, with his slider and fastball being the two main talking points. To round out the arsenal he hurls a curveball just above 80 mph with two-plane break.
Slaten also used to possess a five-pitch arsenal, but he ditched a changeup that most scouting reports say he lacked feel for and was a below-average pitch overall. Drafted in 2019 out of New Mexico by the Rangers, Slaten was actually a starter in Texas’ system until early in 2022 when he moved to the bullpen. He consistently had impressive K/9 numbers as a starter throughout his time in the system but could never figure it out results-wise, so he was moved to the bullpen. He still ended 2022 with a 6.93 ERA in Double-A despite an 11.37 K/9, but the move began to pay off in ‘23 as he had a 3.16 ERA in 35 outings/51 IP at Double-A — before finishing the year with 8.1 innings in Triple-A, where he allowed just one run.
Luis Guerrero
Luis Guerrero had a rise through the Red Sox system and rankings in 2023, as he was expected to begin the season in High-A Greenville but a great spring training had him start the season in Portland. The 23-year-old Dominican-born arm could see time at the big-league level this season after the righty dominated the Double-A level and made it to Triple-A by the end of the season despite some lackluster control.
Guerrero sits 96–98 with the fastball at a mid-4° VAA and a dead-zone 14" of ride/11" of run with his three-quarter arm slot, while he can occasionally touch triple digits. He struggles with both control/command but the pitch has a plus upside due to its characteristics and raw stuff.
His splitter I really, really like. Its spin rate is in the 800s and it has a strong ability to generate whiffs, though it is thrown sparingly with a rather inconsistent feel for it. Guerrero then flashes two slider profiles as secondaries, one being a tighter Slutter-like gyro at 87–90 and the other being a more of a sweeper shape in the low-to-mid 80s that can reach as far as 15" of sweep (averages around 10"); the sweeper seems to be a new addition this season based off his older scouting reports. Both show an ability to miss bats and solid potential.
The control as mentioned though is very questionable for Guerrero with him putting up a 5.44 BB/9 in Double-A this season — he walked nearly a third of batters faced in his six outings at the Triple-A level too. He has some of the best raw stuff in the organization and it gives him a ceiling higher than a 17th-round pick out of a JUCO would usually have, but the control could be what holds him back from reaching his ceiling.
Ryan Fernandez
Ryan Fernandez was scooped up by the Cardinals in the Rule 5 after Boston chose not to protect him, and there’s a moderate to decent shot Fernandez sticks in St. Louis for the year. The 25-year-old right-hander had a 1.77 ERA in 14 outings for Double-A Portland but got shelled when called up to Worcester, slating a 6.16 ERA in 26 games though still displayed a strikeout ability with a 10.27 K/9 and limited walks fairly well despite his struggles at a 2.9 BB/9.
His fastball averages 95–97 while topping out at 99, though on the negative side of things he gets just 14" of ride at a -5° VAA. He had a solid in-zone rate but struggled to command the pitch with some really ugly EVs at the Triple-A level. It‘s thrown as a four-seamer but can often flash more sinker-like shape with a bit of run and ground ball rates at the bottom of the zone.
As for the rest of his arsenal, it features three pitches with 1–5" of horizontal movement that have plus spin rates. The true cutter sits low 90s and has a chase+whiff ability, while the gyro slider is mid-to-high 80s and is just a slower version of the cutter with less ride. He rounds out the arsenal with a low-80s curveball that has low in-zone rates and is thrown sparingly but can get whiffs.
With not much success at the Triple-A level in 2023, it might be tough for him to find success in the majors with St. Louis but he certainly has the upside due to his raw stuff and he keeps runners off via balls at a decent rate to where he could salvage a nice bullpen role with the Cardinals.
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