Luke Weaver: A Perfect Fit for the MLB Winter Landscape


This year’s Winter Meetings are about to shine a spotlight on this season’s greatest deficit — lost revenue. While every club in every market took a hit from diminished television revenues and no fans in the seats, the signing ability of various clubs has never been more challenging. Now more than ever, everyone will be looking for value players. Big money acquisitions of high profile free agents may no longer be viable for anyone except for clubs with deep pockets — and some may choose to forgo these investments depending on the  growth cycle of their organization. Similarly, smaller markets and clubs with limited pocketbooks still need to find value at the right price to help get their team to the next level. The most obvious way to accomplish this is via trade — typically, clubs will look for players with a decent amount of control at a low cost. While both of these factors may result in the need to dump off more prospect capital, clubs with deep farm systems and solidified, controllable pieces at the big league level can accomplish this with ease. With quality pitching particularly sparse this offseason, there is no better candidate for one of these trades than Luke Weaver.

There are a lot of things pointing towards Weaver being an ideal trade target. Before diving into why he is such a fantastic option, the trade partner must be discussed. Heading into 2020, the Arizona Diamondbacks looked like a team poised to make a postseason push. They had won eighty-five games in 2019, while adding Starling Marte and Madison Bumgarner via trade and free agent signing. However, 2020 exposed their lack of depth in relation to the powers of the top-heavy National League. Bumgarner struggled while dealing with injuries, Ketel Marte did not produce at the near MVP rate he did in 2019 (though he was still solid), and the top-heavy nature of the roster saw the club struggle to keep up with the Dodgers, and the rejuvenated Padres in the West. While the club likely isn’t looking to sell (they have a good farm and a solid core led by a controllable star – Marte), the one position they can cash in at is pitcher. The D-Backs have a ton of farm depth on the hill, and if the club stays on course, they could be a real threat in three or so years in the NL. Unfortunately for Arizona, their situation in the corner infield is what needs to be addressed to realize that future success. Right now, they only have one organizational top thirty prospect that plays either spot (Seth Beer 1B/OF). The end goal is not to reach the postseason, it is to win championships. The Diamondbacks are not poised to win a title in 2021; while the playoffs would be a great step forward, taking a step back for one year, in order to build a team that can contend for a title in three years, is worth the sacrifice. Trusting in their player development system and getting a massive return at one of the positions of need (T-50 Prospect plus additional piece or two) would be very helpful in taking steps towards a title. The 27 year old Weaver is set to make 1.9 million in 2021, and is under control through 2023. Three years of control for a minimum number three starter (see below) could bring in that type of haul.

Why Weaver (Intro to Assessment)

While the age, price tag, and control are already enticing for a prospective buyer, Weaver’s reliability, output, and room to grow make him even more attractive. Although he has had some up and down seasons, there is a direct correlation seen in his data that explains his shortcomings. Even without optimization, Weaver is a reliable middle of the rotation arm, having posted an xERA between 3.58 and 4.72 since his rookie year. As mentioned prior, the 27 year old has a lot of room to grow — as seen by his mechanical traits. Based on the pitch adjustments/characteristics he has made, Weaver could become a cost effective number two caliber starter in short order. Below, we will go step by step on how this optimization can be accomplished, further justifying a trade inquiry. 

The Assessment

Before diving into his current pitch traits and their ideal optimization, it is critical to assess what the arm physically does and what his biomechanical data (and the eye test) tells us will be best for him. This is the only way to fully create a plan of attack for maximization.


Weaver’s elite hip/shoulder separation is a major player in his ability to generate power (Graphic via Robby Rowland)

Mechanically, the 6’2’’ 170 Weaver does everything he can to generate maximum velocity on his pitches. Upon the apex of his gather, Weaver coils his hip back, resulting in the far left part of his left glute pointing directly at the plate. This movement positions Weaver to create maximum kinetic energy as he comes down the hill. While the quality momentum generator serves him in the output department, it does not help him in creating an elite extension of any kind — Weaver’s extension sits at an average 6.04 feet. While this is not ideal in creating a plus vertical approach angle for someone of his stature, but he makes up for it with his solid hip flexor mobility and lower half strength. Upon plant, Weaver sinks very low into his glutes. This not only helps make up for some of the potential release height issues (bringing it down to 5.68 feet – more than adequate for a fastball thrower), but also helps him maximize his power through the use of his entire lower half. After his sink, Weaver does a very good job of delaying the start of his arm action, which allows him to be on time and create elite hip/shoulder separation (another major player in power production). His solid scap retraction suggests high velocity as well, leading to the conclusion that Weaver would ideally be a fastball thrower. The power generation, clean repeatable mechanics, and relatively low release height coming from a mid to high ¾ slot (plus for Vertical Approach Angle type of arm, not elite) all point towards him being a fastball/curveball based starter — when optimized.

Weaver’s Pitch Chart in 2020


As his delivery traits suggest, Weaver relies on a four-seam fastball as his primary offering. The pitch averages 94 mph, topping out at 97.2 with a spin rate of 2467 rpm. A mid 90s fastball with a spin rate in the upper 2400s (elite) plays right into the notion of the vertical approach angle based, flat fastball thrower. The high amount of magnus force generated on the pitch resulted in it getting 2.6 more inches of lift than an average big league fastball in 2020. While these traits are already a plus, Weaver also knows how to use the fastball to be most effective. Locating the pitch at an average height of 2.58 feet, he prefers to spot it up in the zone, where he can generate more whiffs (20.4%). 

There is not much more that needs to be done in order to optimize Weaver’s fastball — he made significant adjustments to improve the pitch between 2019 and 2020; and, the data shows that its traits significantly improved. In 2019, Weaver’s fastball was thrown at an efficiency of 85.6 percent. What came with this was more drop on the fastball and less induced vertical movement. Weaver corrected this last offseason, bumping the efficiency up to 91.4 percent, and it showed improvements in its movement profile and traits across the board. While his expected stat values didn’t change much between 2019 and 2020 (xBA, xwOBA slightly better, BABIP over 50 pts worse despite the improvement of the pitch), this can be attributed to the combination of excessive fastball usage (54% of all pitches were fastballs), and counterproductive changes he made to his offspeed arsenal (particularly the cutter and curve, which forced him to use the pitch more often). 

Weaver’s fastball can be deadly when he is on – the traits support it. With a fully developed arsenal, it woul


Weaver’s primary offspeed compliments his fastball beautifully. While its movement profile is nothing to raise an eyebrow over, his unique, yet solid changeup plays borderline elite (.214 xBA, .265 xwOBA, 34.9% whiff rate, .252 BABIP). What makes the 84.6 mph changeup special is that it is relatively low spin (1666 rpm average). While this would lead one to believe that the pitch would drop off the table, it does not get much induced vertical break or gravity included drop at all (4.1 inches of drop less than MLB average changeup). Normally this would hurt most changeup’s effectiveness (particularly low spin variations), but Weaver’s offering resembles a poor man’s version of the Ian Anderson changeup — even though the seam orientation itself does not mimic the fastball like Anderson’s, the movement profile, ability to tunnel, and change in velocity alone makes it effective because the pitch looks like a meatball, with hitters getting caught out in front. 

The changeup does not need to be adjusted whatsoever. It is proven, effective, and it’s  Weaver’s best offspeed pitch. The only issue that Weaver could run into with the changeup is the same problem that the fastball faces — overuse. Due to the shortcomings of the cutter and curveball, Weaver was forced to throw a changeup on 27% of his total pitches thrown in 2020, higher than any year prior. This coincided with the further regression of his two other offspeed pitches. 

While the 2:00 axis helps Weaver garner some horizontal movement, it is relatively nominal. The change in velocity, along with how well it tunnels is what makes it a dangerous offering.


.308 BABIP, .295 xBA, .590 xSLG, .389 xwOBA, 90.1 mph avg Exit Velo in 2020

Weaver’s cutter needs significant adjustments. His cutter profile (88.3mph, 2360rpm) has changed greatly over the last year; in 2020, it averaged 23.7 inches of drop, and 2.5 inches of cut. This was drastically different from his 2019 cutter, which showcased 28.8 inches of drop and 3.4 inches of cut. Succinctly, his 2019 cutter was highly effective compared to his 2020 version; also of note, the spin rate was slightly higher in ‘20, which would account for the loss in gravity induced drop. Surprisingly however, he lost horizontal movement on the pitch when the spin rate went up — suggesting that other factors were at play. Thankfully, the issue was easy to spot; it was his spin efficiency. In 2019 (when the cutter played plus), Weaver threw it at a very low efficiency, almost similar to a slider at 36.6 percent. In 2020, he bumped the efficiency up to 51.5 percent. The sudden change in efficiency hurt Weaver’s cutter, taking away from its break profile due to a loss in gyro action (desirable for a cutter or slider- Weaver’s was pretty much a slider). This alone is likely not the only change that must be made to optimize the pitch. While the change in efficiency would explain some of the differences in movement profile, the decrease in vertical drop (gravity included) with more efficiency (2020) is likely a result of a slight vertical shift in pitch axis as well. After checking Weaver’s cutter data, this held true. In 2020, Weaver’s cutter was thrown from a 12:00 inferred axis. How did the movement profile change with the perfectly vertical tilt? He lost 0.8 inches of horizontal cut — the major caveat here is that Weaver has yet to throw his cutter from a horizontal axis. If he shifted it to a quasi slider (10:30 ish tilt), he could end up with a very sweepy look; coupled with bringing its efficiency down to get the desired gyro effect, the cutter could become a real weapon.

With a changeup that already mirrors the fastball (doesn’t move a ton), the ability to generate a pitch with plus horizontal break to the glove side would make Weaver’s arsenal more dangerous; it would also allow him to cut back on his fastball and changeup usage, which should in turn help in their effectiveness.

The cutter variation seen in St. Louis was lower efficiency, and geared more towards horizontal cut to the glove side. This type of bite, along with a more horizontal axis would help revamp and maximize the pitch’s potential for his arsenal


.500 BABIP, .412 xBA, .581 xSLG, .403 xwOBA, 90.9 mph avg Exit Velo in 2020

Weaver’s curveball, which showcases a poor 6.2 inches of horizontal break less than big league average is also in a strange spot. He throws the pitch at 55.3% efficiency, suggesting that it should have a very slurvy movement profile when coupled with its 7:00 inferred axis. However, this is clearly not the case. An ideal curveball should be a high efficiency pitch in order to generate max depth — if we apply this to Weaver, it means that there is a lot more potential bend on the pitch that he has yet to access as a result of its efficiency. Despite the low efficiency, his vertical drop on the curve is about big league average at (53 inches). This means that a significant bump up in efficiency (causing induced vertical break) could see it become a plus curveball (55-56 inch range) — giving him four legitimate offerings with proper optimization and player development work. The need for a slurvy breaking ball is not present for Weaver, as he already throws a cutter (glove side break); thus depth should be prioritized. In order to maximize this, he could shift to a twelve-six style of curve, though it is not necessary, and should not be prioritized over the efficiency bump. His attempt at a gyro heavy curveball hasn’t garnered anything remotely positive in regards to horizontal break, so the shift toward a high efficiency, vertical break oriented pitch makes sense anyway (tilt should be optimized for this as well). 

The addition of a plus bender would give Weaver pitches that cut to the glove side and drop heavily in the offspeed department (changeup is a deceptive non-mover). While he located the pitch low in the zone, his current curveball has the potential to go from average to plus. Being able to use it more often (and reliably) would again bolster the effectiveness of the other pitches in his arsenal. 


Luke Weaver presents as one of the most attractive potential targets for clubs in need of pitching help for 2021. The combination of his mechanics and elite fastball traits provide a solid foundation; when paired with his plus changeup, and the room for growth on both the cutter and curveball, Weaver could present himself as a plus three to number two arm at only 1.9 million for next year. With three more years of club control, teams with deep farms (and big league ready, higher caliber prospects) should look no further for a solution to rotational depth issues heading into next year.

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