Adrian Morejon, The Starter
Lugo, King, Morejon. The San Diego Padres are going to do it again!
Introduction
An area of Major League Baseball which always intrigues me is roster utilization. In particular, how teams will adapt their current pitching depth to maximize their value in the upcoming year. One of the most common examples of this is transitioning relief pitchers into starter roles. We have seen fantastic results in this department, with Michael King and Garrett Crochet being the most prominent examples during the 2024 season. Of course, it doesn't always work out, with AJ Puk and DL Hall being much better out of the bullpen.
Kyle Boddy, the founder of Driveline Baseball, expresses a similar sentiment in terms of converting relief pitchers into starters, and explains the integral role that scouts play in this process. Some pitchers simply have characteristics that allow them to excel as starters, which are difficult to assess through data alone.
Determining which pitchers are capable of making the transition gives teams a massive competitive edge over their opponents. After all, maximizing value is the name of the game in professional sports.
I dove deep into the data and the tape to determine which pitchers have the skill set to make the jump in 2025, and one name that continuously stuck out was Adrian Morejon of the San Diego Padres.
Adrian Morejon presents an interesting case for moving to the starting rotation. Let’s dig deep into Morejon and see why I believe he is the next RP to SP success!
Adrian Morejon, The 25-Year-Old Veteran
Morejon is a 25-yaer-old RP on the San Diego Padres. He has signed out of Cuba at 17 and was subsequently thrust into a starting role in San Diego’s minor league system just a year later. He was extremely effective throughout MiLB career, making 43 starts before his MLB debut in 2019 at just 20-years-old. Since then, Morejon has been used sparingly in a starting role, with most of his appearances coming out of the bullpen.
A combination of injuries and poor performance limited Morejon’s MLB experience. Prior to 2024, he tossed 75.0 IP while posting a 5.28 ERA and 4.78 FIP, with 2023 being his least productive season of his already 5-year career. From all accounts, it looked like he was slipping out of favour in the Padres bullpen; he simply wasn’t performing.
Fast-forward to the end of the 2024 season, and we see that not only has Adrian Morejon carved out a role on the Padres, he was one of the most successful relievers in baseball. He posted a 2.83 ERA and 2.79 FIP across 63.2 IP while being consistently dominant in any leverage situation. Thanks to his previous starting experience, he has the endurance to pitch multiple innings if required, and did so multiple times throughout 2024.
Let's take a look at what changed from 2023 to 2024, and how these changes pave the way for Morejon to be an effective starting pitcher in the future.
Adrian Morejon, The Inconsistent Stuff Artist
Adrian Morejon has always been a stuff-heavy pitcher. According to my tjStuff+ model, Morejon’s 4-Seam Fastball and Slider combination were amongst the best duo in 2023. Each pitch graded out at 107 tjStuff+, which means that both offerings were plus-pitches.
While he had a very strong Fastball-Slider combo, Morejon was essentially a 2-pitch pitcher. Without a refined off-speed pitch, he struggled immensely against RHH, as they sat on his fastball and crushed it. It wasn’t a large sample, but in the 26 RHH Morejon faced in 2023, they returned a .491 wOBA and walked as often as they struck out.
Another weak aspect of Morejon’s performance in 2023 was his command. He had no issues pounding the zone with his fastball and slider, but he struggled to generate chases, which inflated his BB% to 11.4%. His inability to generate chases led to a poor Whiff% as batters consistently swung at favourable pitches. These results were easily explained by his astronomically high 89.5 Z-Contact% and pitiful 17.1 O-Swing%
Adrian Morejon, The Experimentalist
It was clear that Morejon's arsenal wasn't working. He had the stuff foundation, but the execution and lack of depth made him very susceptible against patient batters. Morejon went into the lab during the winter and returned with a revamped arsenal and delivery and the determination to make the Padres bullpen.
Morejon came out of the gate firing. For starters, he was throwing much harder than in 2023. His velocity bumped up from 95.3 to 97.4 mph, which placed him amongst the highest velocity arms in the game. Morejon lowered his release as he reintroduced a sinker into his arsenal, swapped his changeup for a splitter, and completely dropped his curveball.
There were a ton of changes. And they worked!
The Geometry Wiz
Let's look at Morejon altered his delivery.
Morejon had a 54° arm angle at release in 2023. This aided the ride on his fastball, but limited the horizontal break on his slider. This season, he lowered the angle to 43°, which is closer to his delivery earlier in his career.
As Jeff Sanders reported back in April, this change was largely due to analyzing Morejon’s biomechanimcal data. San Diego Padres pitching coach Ruben Niebla highlighted an important aspect of Morejon’s delivery that likely hindered his production and impacted his health:
With the new biomechanics lab at Point Loma Nazarene among the data points at his disposal, Niebla discovered that Morejón’s rotational plane had fallen out of sync with his arm.
Essentially, Morejón’s torso was going one way and his arm was going another, leading to both inconsistencies in his delivery and extra stress on his arm, which may have been contributing factor to spending so much time on the injured list.
To resync the delivery, Niebla had Morejón lower his arm slot to a spot that Morejón was at four years ago.
Thanks to this change, Morejon remained healthy throughout the entire 2024 season. This change also helped transform Morejon into an E-W pitcher by allowing him to more readily add in a sinker and sweeper. The addition of the sinker may be the biggest driver to Morejon's success this season.
The Sinker Savant
Morejon sporadically tossed his sinker throughout his career, but it was never a staple in his arsenal. In 2024, he used it as his primary fastball against both handedness, but exchanges it's usage for his 4-Seam against RHH. A new pitch to tackle both LHH and RHH was a smart decision, and he amplified it's effectiveness with his command.
Morejon’s tendency to pound the zone works well with a sinker because the offering is designed to induce weak contact. He tactically locates the pitch in the inner third against LHH early in the count. This leads to a lot of called strikes and poor swings. It returned a 34.9 CSW% vs LHH, and perfectly sets up his devastating slider to put away batters.
The offering has also been effective against RHH thanks to Morejon's tendency to keep the pitch in the bottom half of the zone. The usage is lower, but it's a similar approach with Morejon opting to use it early to get strikes and behind in counts to even it up. Weak contact is the goal, and it has worked out flawlessly.
The Slider Specialist
Morejon's slider is his most valuable pitch according to Baseball Savant Run Value, and his execution improved tremendously this season. He utilizes his slider as a put-away pitch, and has been proficient at painting the corners of the zone.
Against LHH he tosses it low and away, and low and inside vs RHH. This has led to a stellar 39.8 Whiff%; a massive jump from 2023.
The movement of Morejon's slider is unique as it drops significantly more than an average slider while also being faster. Another beneficial aspect of the offering is that it gets above average horizontal movement. Thanks to its velocity and movement, it is an effective offering against both LHH and RHH.
The 4-Seam Fader
Thanks to the reimplementation of his sinker, Morejon has relied less on his 4-Seam Fastball. His 4-Seam has statistically been his least effective pitch since entering the league, and decreasing the usage seemed necessary.
The 4-Seam production this year hasn't been ideal, but its Whiff% has spiked and it's overall effectiveness improved. This improvement can be explained by his tendency to attack the top of the zone with the offering.
The Splitter Strategist
We've seen the changes that Morejon made to better tackle LHH and improve his overall productiveness, but the biggest piece to the puzzle for a lefty starting pitcher is an effective Off-Speed pitch to handle RHH.
Thankfully, Morejon introduced a new splitter into his arsenal, which looks to be a game changer into his prospects as a SP. Morejon always had a changeup in his back pocket, but he seldomly tossed it, likely due to his high usage against LHH out of the bullpen. This season, Morejon was tasked to face a lot more RHH, and his results were great, posting a 3.09 FIP across 163 PA. Let's see how the splitter helped.
As you would expect, Morejon exclusively used the splitter against RHH, at ~12% Usage Rate. It was also used as a put-away pitch. Morejon’s command has evolved over his career, and his splitter may be his most impressive development. He tunnels it well with his sinker, and it drastically veers downwards as it reaches the plate, resulting in some nasty whiffs.
On the season, it has a 58.1 Whiff% against RHH, and more impressively, the pitch has been effective at inducing weak contact. It's a brilliant pitch, and it will be the key to transforming Morejon into an effective starter.
The Sweeper Student
Morejon’s lowered his arm angle, which has allowed him to more easily add in a sweeper as another weapon against LHH. It is a very new pitch, and with just a ~3% usage and it is clear that he is still getting the feel for the offering.
It has ~30” of horizontal break differential with his sinker, which is similar to fellow teammate Michael King, who saw great success in 2024 transitioning from a RP role to a SP role.
Adrian Morejon, The SP Hopeful
Lance Brozdowski outlines a framework for determining which RP could transition into SP.
He states:
Starting point may be to look at RPs with good zone / command stats and 3+ pitches
The Zone Controller
Adrian Morejon deepened his arsenal while honing in his command, which has allowed his stuff to play well in the zone. He has consisntly filled up the strike zone throughout his career, and 2024 was no exception. He sat in the 93th Percentile amongst MLB Pitchers in Zone%, as 54.7% of the pitches he threw hit the zone. This has also helped buoy his 1st Pitch Strike% to 62.7% (MLB Average is 61.0%).
Thanks to the changes to his arsenal, he was able to induce a lot more whiffs this season, espically in the zone. He returned a solid 81.3 Z-contact% (MLB Average is 82.6%). He’s throwing a lot of pitches in the zone, and batters are missing at an above avearge rate. That is a recipe for success.
The Flexible Lefty
Following the 2024 season, the San Diego Padres only have 4 SP (all RHP) under team control (Yu Darvish, Michael King, Dylan Cease, and Joe Musgrove) with Martin Pérez (LHP) as a pending UFA. The Padres also empited their farm to bolster their bullpen for the playoffs.
In other words, the Padres need a starting pitcher!
Morejon fits the mold well. He has the arsenal and the proir expierince to transition into a starter role. His low expected salary (Arb 3) allows the Padres to be flexible with signing their arbitration eligbile players and other free agents.
Conclusion
Morejon has a lot going for him entering the 2025 season, which should allow him to transition into the back end of the Padres rotation:
Opening in Rotation (Pérez FA) ✅
LHP with 4+ Pitch Arsenal, including strong Off-Speed ✅
Elite Stuff ✅
Great In-Zone and Command metrics ✅
The Padres have had great success in transitioning a RP into a SP in recent years. We've seen the success of Michael King as he returned one of the most valuable SP performances this season in his first full year of starting. Seth Lugo in 2023 is yet another example. The Padres scouts and analysts have an eye for targetting pitchers that can make the RP-SP jump, and their coaches have a knack for helping these pitchers reach their potential.
Morejon has the tools to succeed in a starting role, and the Padres have the track record to make it happen.
Thank you for reading!
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