Atlanta Braves rookie starter Spencer Schwellenbach impressed in the 2024 season. After being called up to the big leagues in late May, Schwellenbach was one of the best starters in baseball posting a 3.35 ERA and 1.04 WHIP across 123.2 innings. Furthermore, he displayed elite control and command with one of the ten lowest walk rates at 4.6%, tied with AL Cy Young favorite Tarik Skubal.  He complimented this exquisite command with a strong strikeout rate as well at 25.4%.  Overall, he showcased an impressive and complete profile that bodes well for his future.

Complimentary Arsenal

Schwellenbach adopted a similar theme among starting pitchers across MLB in that he threw a variety of pitches. He threw six different pitches at least 5% of the time, including three variants of fastballs. The ability to throw multiple fastballs is a big difference maker in preventing hitters from keying in on the high four-seam fastball that everyone is looking for. This element of unpredictability played in Schwellenbach’s favor as he was in the 96th percentile in Chase%. Meaning, he was getting hitters to chase outside the strike zone at one of the highest rates. While he utilized a kitchen-sink type of approach, this was not due to a lack of quality stuff.

By Stuff+, Schwellenbach possessed three above average pitches. Those included his four-seam fastball, slider, and curveball.  Additionally, it is not as if his other three pitches were poor. His sinker, cutter, and splitter were merely average to below average.  The feature that makes Schwellenbach unique is his lower release point. He throws all of his pitches from roughly the same height at 5.5 feet.

Usage Tendencies

Schwellenbach’s four-seam fastball does not get exceptional vertical movement numbers, but this low release height enables him to get to a flatter plate in terms of approach angle. He throws this pitch roughly 30% of the time. When he is able to locate it at the top of the zone, it can have a good amount of success. When he misses his spot and leaks into the heart of the zone, he is more susceptible to give up damage.  While it grades out well by Stuff+ (110), it generated roughly an average amount of swing and miss.

Schwellenbach uses his cutter almost interchangeably against each handedness of hitter and curiously performed much better against right-handed hitters. Further, sinkers are commonly added to an arsenal to improve against the same handed hitter. Interestingly, Schwellenbach’s sinker was his worst performing pitch against right-handed hitters by a significant margin. Although, it did serve a purpose in being his highest ground ball producing pitch. Furthermore, his curveball produced strong swinging strike rates against both hands. Perhaps his best pitch, Schwellenbach’s downward slider dominated both hands and he could increase its usage against left-handed hitters. Lastly, his splitter was used almost exclusively versus left-handed hitters and returned exceptional results.

Areas For Improvement

As mentioned previously, Schwellenbach had rather stark splits against each hitter handedness. He dominated right-handed hitters with a .581 OPS.  On the other hand, left-handed hitters had a .743 OPS. Primarily using his four-seam and slider against right-handed hitters, he was more varied against the opposite hand.  It looked like he was reluctant to overuse his slider against left-handed hitters (only 9.2%) despite its excellent results. Schwellenbach’s slider possesses great depth shape with little horizontal movement. This shape is more platoon neutral, and given how well it performed when he used it (22.7% swinging strike rate), he could justify ticking it up more. His four-seam and cutter were hit for a lot of damage against left-handed hitters. Conversely, his splitter, the worst graded pitch by Stuff+, proved to be an invaluable weapon against lefties. So, a possible plan could be to maintain his splitter usage, decrease the four-seam and cutter usage, and bring up the slider usage.

An important element to keep in mind with the young Braves starter is his lack of experience pitching. He was a two-way player out of Nebraska pitching only 30 innings in college. For him to be this refined out of the gate is remarkably impressive. There will always be aspects to improve on. However, his propensity to avoid walks and generate strong swing and miss rates is an outstanding foundation.  A potential drawback of his elite strike throwing is that he can live in the zone too much. As a result, it can leave him more susceptible to giving up hard contact.  With his ability to induce swings outside the zone, he could afford to bring his Strike% down a touch.

Future Outlook

Schwellenbach is a great athlete who already seems to have an advanced feel. He came up to the majors throwing three to four pitches and by the end was throwing six. Remarkably, he learned the pitch in a bullpen session and then was throwing it in his next start.

Spencer Schwellenbach added a new pitch to his arsenal😏

@HannaRaeYates has the full report. pic.twitter.com/S9Eg590fRv

— FanDuel Sports Network South (@FanDuelSN_SO) June 18, 2024

This also shows a willingness to adapt to how hitters are approaching him and evolve his game. In addition, he made an adjustment on his four-seam fastball grip to improve its shape. It is a subtle tweak but makes a substantial difference in how hitters perceive it.

Apologies for the awful camera work, but you can still see how tonight’s Braves starter Spencer Schwellenbach changed his fastball grip to kill horizontal movement and make it stranger (and tougher for hitters) with respect to his arm slot. Bonus is his curve grip change. pic.twitter.com/VmwqGFGO0b

— Eno Sarris (@enosarris) August 16, 2024

Altogether, it was an impressive rookie campaign for Spencer Schwellenbach. He showed many foundational elements that you want to see from a young starting pitcher. His strong surface level numbers were backed up by excellent peripherals. His 3.42 SIERA was a top 15 mark in all of baseball (minimum 120 innings). That would be an impressive season for any pitcher let alone a rookie.  Already flashing this level of upside and a solid inning total, Schwellenbach has an opportunity to be even better in 2025 as he gains more experience. He has all the makings of a future ace in the big leagues.