2018 MLB Draft Mega Injury Preview

By Dr. Ankur Verma


Credit: slgckgc on Flickr.

The MLB draft is on Monday June 4 this year.  As a draft junkie, it’s appointment television for me.  But for the MLB draft in particular, I’ve always been fascinated by the proceedings.  Teams can’t trade draft picks and many times picks are made for signability issues due to each team having a certain spending cap.  So it’s just fun to watch it unfold.  And, of course, there is always injury drama.

I decided to go through the top 32 players on ESPN’s Keith Law’s 2018 Big Board (as of May 24, 2018) and highlight a few prospects that have potential injury questions.  As always, we’re not privy to medical information and considering these are college and high-school baseball players, have even less to go on.

Casey Mize, RHP, Auburn (Law Big Board Rank: 1)

Casey Mize. (Credit: Brandonrush).

The presumptive Number 1 overall pick of the 2018 draft brings an interesting debate to the table.  One of the reasons he is so effective as a prospect is his split-finger, which several publications rate as a “plus-plus”.  And yet… Mize has a history of arm troubles, ranging from “arm fatigue” to arm flexor strains to, most recently, a vague “ongoing issue with his right arm“, which resulted him being scratched from a start as recently as May 18.

First, let’s dive into this question: is the split-finger the cause of Mize’s various arm troubles?

According to this article by the Star Tribune, former Minnesota Twins pitcher Eddie Guardado attributes his heavy usage of the splitter to his Tommy John surgery.  In fact, the article states that the Twins don’t let the pitchers on the lower rungs of their farm system use the pitch in an effort to preserve elbows and so do the Red Sox to some extent.

Is there any merit to this?  Below is a table of major league pitchers from 2014-2018 who used their splitter at least 10% of the time (Mize uses it about 16% per Fangraphs) and their history of arm issues, if any:

MLB Pitchers with Splitters 2014-2018

Name%SplitterShoulder/Arm/Wrist troubles?
Matt Shoemaker27.5Forearm, multiple times
Masahiro Tanaka27.3Elbow (UCL), forearm, wrist, shoulder
Alfredo Simon25.5Tommy John, biceps, shouler
Hisashi Iwakuma23.1Shoulder
Kevin Gausman18.1Shoulder
Ubaldo Jimenez15.7None
Miguel Gonzalez15.4Tommy John, shoulder
Homer Bailey15.0Tommy John, forearm, shoulder
Mike Pelfrey14.7Elbow
Tim Hudson12.7Tommy John, shoulder
Dan Haren11.5Shoulder
Ricky Nolasco10.6Elbow
Jeff Samardzija10.3None
%Splitter= % of pitches that were splitters
*Only pitching arm was considered
*only time on DL/missed starts was considered


Caveat to this list: there’s survivorship bias here.  Since we’re only looking at major league pitchers, we’re not including all the minor league pitchers that may have a splitter as their dominant pitch but got rooted out of professional baseball due to arm troubles.  Also, I’ve only categorized major league pitching injuries and haven’t looked into their injury history in the minors.  Still…splitters look bad, don’t they?

Well, hold that thought.  Let’s take a look at the 13 pitchers over that same time span who relied the most on their fastball:

MLB Pitchers Relying on Fastball The Most 2014-2018

Name%FastballArm/wrist issues?
Bartolo Colon84.5Elbow, shoulder, arm
Lance Lynn81.4Tommy John, forearm
Aaron Sanchez74.9None
Jarred Cosart71.2Elbow
Juan Nicasio70.9None
Clayton Richard70.9Shoulder
J.A. Happ70.8Forearm, elbow
Mike Pelfrey68.4Forearm, elbow
Danny Salazar68.4Elbow, shoulder
Tony Watson68.3None
Josh Collmenter67.5Shoulder
Tyler Chatwood67.4Tommy John, arm
Shelby Miller67.4Tommy John


Hmmm.  Well, these lists look alike.  The truth is, despite its shaky historical reputation, precious few studies exist that study the differences between a splitter and a fastball in terms of injury risk.  However, there are several studies that look at other off-speed pitches.

Glenn Fleisig of the American Sports Medicine Institute conducted a study in 2016 where he looked at fastballs, curveballs, and change-ups of more than a hundred pitchers at various levels and found that shoulder and elbow stress was actually greater in fastballs compared to change-ups and that curveballs did not differ from the other two pitches.  Additional research, presented here by Driveline Baseball, indicates similar findings.  However, Driveline, using their Motus Sleeve technology, found that when they normalized stress for velocity among different pitch types, curveballs and sliders actually proportionally added more stress to the arm than fastballs.  Less torque overall, but more stress when controlling velocity.  Driveline suggests investigating the distribution of forces among forearm muscles, given that the forearm is held in supination longer for curveballs.

Kyle Boddy has employed electromyography testing for the past few years to investigate muscles in the arm during the act of pitching.  He has found that spin-rate changes are a great predictor of injury; unfortunately, I do not have access to any spin rate data for Mize.  As Boddy points out, the flexor carpi ulnaris and flexor digitorum superficialis alone combine for a quarter of the stabilizing force against the valgus stress on the elbow.  The next step is likely using electromyography to investigate the distribution of forces along the flexor-pronator mass of the forearm during splitters compared to other pitches.

Flexor-Pronator Mass. (Credit: CFCF).

With that said, though, of greater concern for the risk of injury may be velocity.  Jeff Zimmerman at The Hardball Times found that the harder pitchers threw, the more likely they are to make a DL-trip the following season.    Mize’s heater generally sits 93-95 (though can go as high as 97), so he seems a slightly above-average risk of injury from that standpoint.

Of course, none of these studies examine the splitter specifically.

Back to Mize.  For what it’s worth, he blames his arm troubles on his slider, which led to him alter his grip on it this season.  Again, for what it’s worth, he was scratched from a May 18 start due to arm fatigue, his third missed start in five weekends.


Nick Madrigal, 2B, Oregon State (Law Big Board Rank: 10)
Jake McCarthy, OF, Virginia (Law Big Board Rank: 20)

Credit: Oregon State University.

The diminutive (5-7) second baseman Madrigal missed more than 20 games with a hairline fracture in his wrist after a collision at home plate.  When he played, he slashed an impressive .395/.460/.560 with a microscopic strikeout rate.

Meanwhile, McCarthy also had a collision causing a wrist injury, this time in the outfield when attempting to catch a fly ball.

It’s unclear which bone(s) the fractures are (though it’s curious that Madrigal’s was called a hairline as hairline fractures are generally associated with repetitive stress rather than an acute injury; possibly he just had a small crack in the bone), though it’s worth noting that Madrigal was initially announced to miss three-to-six weeks, while McCarthy was originally announced to miss six-to-eight weeks, which would indicate that McCarthy’s injury was slightly more severe.  Both players eventually returned to the lineup.

Can we expect these wrist fractures to affect their production going forward?

Let’s take a look at batters from 2014-2017 who sustained a fractured wrist and their batting statistics before and after.  As a measure of batting, I am using on-base percentage and isolated power.  On-base percentage because this will give us an idea of player’s ability to get on base and isolated power because I want to look at how power is affected strictly. This list isn’t exhaustive as we do not know the exact nature of the wrist fracture and so are only left with general information.  To get a little more granular, I also included whether the fractured wrist is at the the top of the handle of the bat or at the bottom.  Both Madrigal and McCarthy suffered left wrist fractures, but since Madrigal is a right-handed batter, his left hand abuts the end while McCarthy’s, a left-hander, is at the top.

Batters with Wrist Fractures 2014-2017

NameBat?OBP BeforeOBP AfterOBP ChangeISO BeforeISO AfterISO Change
Josh WillinghamBottom.359.340-.019.215.189-.026
Ryan LavarnwayBottom.
Wil MyersTop.363.328-.
Mike OltTop.
Marlon ByrdTop.330.306-.
George SpringerTop.350.360.01.215.209-.006
Jayson WerthBottom.368.326-.
Maikel FrancoBottom.321.294-.027.189.177-.012
Max StassiBottom.386.331-.
Cameron MaybinBottom.313.344.031.115.1150
Alex GordonBottom.347.309-.038.165.131-.034
Mark ReynoldsBottom.326.355.
Chris HerrmannTop.
Micah JohnsonTop.299.200-.099.0380-.038
Freddie FreemanTop.389.427.038.205.200-.005
J.J. HardyTop.307.310.
Trea TurnerTop.344.368.024.179.172-.007
Players were only included if they had major league batting data prior to the wrist injury


We have to grant a few things: this list is not controlled for age-curves, other injuries,, and league-wide averages in OBP/ISO.  But taking this group as a whole, it appears there is a slight dip in OBP after a wrist fracture.  In fact, the ISO goes up on average.  Taking everything into account, then, it sure seems that there isn’t much difference before and after, right?

Well, if we investigate a little more closely, something interesting emerges.

Top and Bottom Avg

AVG OBP CHANGE-.005-.012


When breaking the players down into whether it’s their top or bottom hand on the bat that’s injured, there’s a big difference in the average change in isolated power (.013) between the two categories.  While the top hands increase their power, the bottom hands decrease.  The list above includes all types of wrist fractures, but research supports that the bottom hand is most affected in hamate fractures.

The hamate is highlighted in yellow.

While the difference between the two groups isn’t statistically significant with this sample size (p=0.30), there is some research to suggest that switch-hitters experience some decline in power after hamate fractures.  Further research by Beyond The Box Score indicates that it takes a full-season’s worth of games for power numbers to return to normal (and sometimes eventually surpass) for non-switch hitters.

In more general terms, The Hardball Times found that wrist injuries seem to weaken swings in a large segment of major league hitters. The caveats to all these studies is the sample size; it’s likely worth investigating with larger samples and at an increasingly more granular level, while also differentiating between types of wrist fractures and strains.  Perhaps the next step is quantifying wrist speed, amplitude, and stress when swinging the bat.

In the case of Madrigal, his game does not rely on power at all.  He contributes in other facets of the game, but his frame doesn’t allow for any power projection in the future.  Therefore, if there indeed is an issue with power decline with wrist injuries, it is unlikely to affect Madrigal’s forecasted big-league ability.

As for McCarthy, things are a bit murkier.  While he hasn’t shown much power at the college level, scouts are optimistic about his ability to tap into some latent power eventually.  For instance, according to MLB Draft Countdown, his current power grade is a 40, while his future power grade is a 55.  MLB.com has a similar story; while they rank his current power tool a 40 as well, they state that some changes in his mechanics could allow him to develop his “raw pop”.  Luckily, he seems to make consistent contact and get on base at a fair clip, all while relying on his speed for other contributions, so even i .  Furthermore, as his top hand was injured, it wouldn’t seem to affect his power numbers anyway, given they actually slightly increase in the small sample above.


Connor Scott, OF, Plant HS (FL) (Law Big Board Rank: 17)

Credit: Ebyabe. Permission: Dual-licensed under the GFDL and CC-By-SA-2.5.

The athletic and lanky high-school has impressed when healthy during the few national circuit games he has played.  Emphasis on few.  Whether it’s due to maintaining some man-of-mystery status as the draft approaches or being slowed by injuries (hamstring, concussion), he hasn’t played in front of scouts that much.  Since this is an injury analysis, let’s focus on the hamstring.

Scott sat out three weeks due to the injury; when he returned he was a designated hitter and did not take the field, which would understandably raise some eyebrows.  As this article from MLB.com explains, during the act of sprinting (important for base-stealing, extra base hits, and covering ground in the vast expanse of centerfield, as Scott is likely to do), the hamstrings contract eccentrically to slow the lower leg and prepare for foot contact and there is evidence that hamstrings are the primary driver of horizontal propulsion.

Which brings us to Scott.  MLB.com grades his run tool at an eye-popping 70 and calls it his “standout” trait.  If his speed is such an important part of his prospect package, will his hamstring injury hamper his ability to be effective?

In order to examine this question, I took a look at players who were placed on the disabled list due to a hamstring issue in 2016 and 2017.  If they had played at least one game in the outfield in those two seasons, they qualified for this list (so some of the players listed aren’t necessarily “outfielders”, per se).  I looked at their Sprint Speed, as measured by Statcast, the season before the injury and the season after (for instance, if a player was placed on the DL in 2017, I looked at his Sprint Speed in 2016 and Sprint Speed in 2018).  Unfortunately, I was unable to get Sprint Speeds for fractions of seasons (leading right up and after the injury), so we have to make do with whole seasons.  This means that if a player had multiple hamstring issues in a season, it was counted as one.  Usual caveat: this probably isn’t exhaustive and may contain errors.  It’s a lengthy list, so make sure to scroll down.

Outfielders Sprint Speed (ft/s) with Hamstring Injuries in 2016-2017 seasons

NameYear BeforeYear AfterDelta
Danny Santana28.828.3-0.5
Ender Inciarte28.127.3-0.8
Danny Valencia27.027.00
Alexi Amarista26.826.7-0.1
Matt Szczur28.328.40.1
Shin-Soo Choo2726.3-0.7
Leonys Martin28.427.8-0.6
Miguel Sano27.726.9-0.8
Hunter Pence28.728.6-0.1
Yasiel Puig28.428.1-0.3
Brandon Guyer28.127.8-0.3
Jorge Soler27.627.70.1
Dexter Fowler28.528.1-0.4
Steve Pearce26.926.90
Chris Young27.727.6-0.1
Lorenzo Cain28.928.8-0.1
Justin Ruggiano26.626.1-0.5
Aaron Hicks28.428.40
Brandon Nimmo28.728.3-0.4
Matt Kemp25.326.31
Mallex Smith29.829.6-0.2
Adam Frazier27.827.3-0.5
Rajai Davis28.929.50.6
Yoenis Cespedes27.127.40.3
Stephen Piscotty27.326.9-0.4
Carlos Gomez29.028.2-0.8
Gregory Polanco27.427.60.2
Chad Pinder27.627.60
Tyler Austin27.327.1-0.2
Howie Kendrick26.726.3-0.4
Aaron Altherr28.8290.2
Willson Contreras28.227-1.2
Abraham Almonte28.228-0.2
Odubel Herrera27.426.7-0.7
Matt Olson24.725.91.2


So it seems the players seem to lose a little bit of steam, right?  Well, according to research by Mike Petriello at MLB.com, about a quarter of MLB players lose about 0.5 ft/s per season.  So over a two season sample size like this, you would expect a decline of about a foot per second, assuming all things equal, in a quarter of these players.  However, few are close to that mark.  So a drop of a mere 0.2 ft/s on average over two seasons seems to be a drop in the bucket.

The MLB average is 27 ft/s.  Virtually all of these players are above that marker.  Fast players seem to generally stay fast, at least in this narrow window examined.

Rajai Davis has maintained his high Sprint Speed with age despite hamstring issues. (Credit: Keith Allison).

Does this mean that a hamstring injury won’t slow you down long-term?  Of course not.  Humans are built differently after all.  Some of the slower speeds could be attributed to a nagging hamstring.  It’s just that there’s not enough conclusive evidence to make a general proclamation that they do.

In other words, I wouldn’t be too worried about Scott.  I didn’t control for age, but if you look at Petriello’s age chart, the younger you are, the faster you are, which makes intuitive sense.  Because Scott is younger than any player on this list, it’ll be a long time (age 33, where MLB players start a steep decline collectively) before we could even start talking about him potentially slowing down.  It’s also possible that things have been tentative with him getting back on the field because the danger of aggravating the injury is extremely costly from a draft-perspective at this point.


Cole Wilcox, RHP, Heritage HS (GA) (Law Big Board Rank: 13)
Shane McClanahan, LHP, USF (Law Big Board Rank: 15)
Brady Singer, RHP, Florida (Law Big Board Rank: 21)
Ethan Hankins, RHP, Forsyth Central HS (GA) (Law Big Board Rank: 31)
Ryan Rolison, LHP, Ole Miss (Law Big Board Rank: 32)

Credit: richmond96.

All of these pitchers have delivery issues that have raised injury questions.

Let’s start with Singer and McClanahan.  The concerns with both are short-arm actions that Law states “puts stress on (Singer’s) shoulder” and has had some scouts questioning their upsides as starters.  When a pitcher short-arms, they are effectively releasing the ball without utilizing the full extension of their arm; it results in “shot-putting” the ball and creates a loss of velocity.

It also seems to be correlated with injury.  Fleisig et al found that timing of shoulder rotation is key; inadequate shoulder external rotation (as in short-arming) places stresses on other areas of the arm and shoulder, leading to a higher risk of shoulder issues or elbow issues (especially at the UCL.  The same also applies for excessive shoulder external rotation).

And lo and behold: McClanahan has already had Tommy John surgery.  When you couple that with the fact he routinely hits the high 90s and can go up to 100 mph (which is what makes him attractive as a left-handed pitching prospect)—and increased velocity leads to higher risk of injury as described above— he is a substantial injury risk.

The two pitchers also function at a three-quarters arm slot, which leads to the age-old question of whether this contributes to further injury risk.  If you take a look at the videos on Fangraphs for Singer and McClanahan, you can see what I mean.

An intensive 2018 study by Sutter et al using video analysis of over 400 professional players to generate a model for injury risk for pitchers found that arm slot (called “path of arm acceleration: in the paper) by itself wasn’t a significant predictor of injury risk, but when taken in conjunction with other components of pitching (mass and momentum, arm sing, posture, position at foot strike, and finish) produces a model that is a significant predictor.

This 2017 study by Michael Sousa-Johnson found that when compared to an overhand delivery, a three-quarters arms slot doesn’t add any more stress to the shoulder and has a decreased lateral trunk lean (increased trunk lean may lead to greater elbow and shoulder stress).

In other words, the fact that Singer and McClanahan throw from a three-quarters arm slot shouldn’t by itself be a worry for injury.  Instead one should take that information and combine it with one’s knowledge of the other parts of their pitching mechanics to guide one’s concern for their injury risk.

The Sutter paper can also help us address, in part, the potential arm health questions with Hankins and Rolison.  Hankins was near the top of draft boards just a few months ago, but has fallen partly due to missing some time with “shoulder fatigue” that may have contributed to decreased performance once he came back.  Law postulates that the arm troubles could have been due to his abrupt finish, short stride, and stiff landing.

With short strides, the concern is that earlier contact of the stride foot on delivery affects pelvic-trunk interactions that can adversely affect the shoulder and elbow.

The Sutter study used pelvic-trunk interaction as part of their video analysis.  They found that body positioning at foot-strike alone was a significant predictor of injury, with increased trunk tilt at foot-strike increasing upper extremity stress.  So there is merit to this claim if Hankins’ trunk mechanics aren’t particularly up to snuff during his stride.

Sutter et al examined position of the trunk compared to the pelvis as part of their video analysis. (Credit: Ron Reiring).

With Rolison, Law’s concern is that he has a cross-body arm action that “anecdotally” may be associated with arm issues.  Sutter measured this to some extent by using finish as a component of his video analysis, specifically using the criteria (among others) of whether the throwing shoulder was located on the opposite side of the lead league and whether it fell below the throwing-side hip during follow-through.  While finish alone wasn’t predictive of injury risk, they state that it could similarly explain pelvic-trunk mechanics at foot-strike and, as mentioned, adverse pelvic-trunk mechanics could place increased stress in the upper extremity.

Finally, Wilcox.  While he has a low three-quarters arm slot as well, of interest here is the “deep arm action in the back” per Baseball America.  You can see this clearly at the 1:00 mark in the second video here.  The Sutter paper looked at arm swing as a component of their video analysis, grading on the spectrum from elbow flexed and hand close to the body to elbow extended and hand away from the body.  Here is a visual.  Wilcox falls closer to the former category (A and B).

What did Sutter find?  Well, arm swing was found to be an independent predictor of injury, with increasing risk as the elbow is flexed and shoulder internally rotated.  This is not to say that teams should be wary of drafting Hankins, but that there is merit to being concerned that his delivery may portend some issues in the future.



It should be noted that all of these players are younger than the major league players we used as comparisons for their injuries.  Theoretically this means that their bodies would be expected to recover quicker. Of course, the holy grail is eventually reaching the point where we can be confident enough to determine whether the body will eventually heal itself from an early injury or whether an injury at an early age portends nagging issues down the line.  Perhaps we’ll never get there exactly, but maybe we can keep getting closer.


Thank you to Fangraphs, baseball-reference, ProSportsTransactions, and Baseball Savant for statistics and injury information.  All statistics through week of May 28.