Article: Can the Red Sox Help Unlock Kyle Harrison?

[Finley Rogan]

Earlier this week, the Red Sox announced the blockbuster trade which sent Rafael Devers to the San Francisco Giants for pitchers Jordan Hicks and Kyle Harrison, minor-league outfielder James Tibbs lll, and minor-league pitcher Jose Bello. Though the trade will continue to be assessed for years to come as fans await how the Red Sox will spend the money that was owed to Devers, it is clear for now that Kyle Harrison is the best piece Boston got in return.

Going back two years, Harrison was viewed as not only the best Giants prospect, but one of the top left-handed pitching prospects across all of Minor League Baseball. Though he has not dominated the majors, Harrison remains highly-touted with an interesting profile. 

Harrison has only started 35 games in his career, and still does not have 200 MLB innings under his belt. His ratios have not changed much in his three seasons with his K% sitting around 22% and his BB% at 8%. From a run prevention standpoint, Harrison hasn't been particularly lucky or unlucky in his career either. On one hand, his BABIP was .308 last season, but he also had a career-high 41% groundball rate. Harrison also got to play at Oracle Park, which is one of the best pitching environments in baseball, and now he will be at Fenway Park, which is the opposite.

Harrison has a funky delivery where the ball comes out of his hand at a 27° arm angle. The comparable pitchers with that slot are Andrew Heaney, JP Sears, and Kyle Freeland. 

(Statcast)

These low slot pitchers who have a solid fastball typically struggle to develop reliable secondary pitches. Harrison falls into the same boat, as he has crazy high fastball usage at 65%, while he only throws the slurve 25% of the time, and the changeup 10% of the time. That is a trend that has not changed for Harrison, who is now in his third season in the big leagues. The stuff on the secondary pitches has yet to be above average, so the Red Sox will definitely be looking to tighten up the slurve and changeup, and perhaps even add another pitch like a sinker.  

Last season, the velocity was down to 92.5 mph on Harrison’s fastball. Even with that low mark, it remained his most consistent and least-hit pitch. This season, the velocity is back up at 95 mph and the results on the pitch have been dominant. So, it is safe to say that Harrison will be as good as his fastball is, which is hardly a revelation for a pitcher who throws it 65% of the time. 

Early on this season across Harrison’s eight appearances, the slurve has been the predominant issue. The pitch has allowed a .381 batting average along with a massive .810 slugging percentage. Those are nearly double the marks that Harrison allowed with the slurve in 2024. The changeup has been the better secondary option this season, but it has still been hit hard, and Harrison only throws it against right-handed batters. This is why the Red Sox will work hard to help Harrison develop something else in his arsenal he can throw, especially so he can have a third pitch against left-handed batters. He'll always rely heavily on the fastball, but he could have three or four average secondary pitches, since the arm slot makes it difficult for any of them to be elite. Andrew Heaney for example, who has a 26° arm slot, throws five different secondaries to go with his primary fastball. However, it is difficult to believe the Giants — a smart and well run organization — have not tried to add to Harrison’s arsenal the past few seasons, suggesting it may not be such a simple fix for the Red Sox.

One glaring positive from Harrison this season has been his command. He does not have enough innings to qualify, but Harrison’s 118 Location+ would rank in the top 20 among all pitchers in baseball. Yes, the sample size is small, and Harrison will likely see his command drop toward his career average Location+ (105), but good control paired with a high-spin fastball presents a more than viable profile start games in 2025.

Regardless of his shortcomings, Red Sox fans should be excited about Kyle Harrison. Although the circumstances of his arrival are unfortunate, Harrison is a young and exciting pitcher to watch, and has the potential to be a good starter in Major League Baseball. He still has to develop better secondary options to keep hitters off balance, but Harrison’s fastball alone makes him worth tuning in to watch. He is in Worcester right now, but eventually Harrison will make his Red Sox debut in 2025, and it will be fascinating to see if there are any tweaks with his pitch mix after he gets to spend time with the pitch lab in Boston.

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