The NBA Combine has wrapped up and the deadline for declaring for the draft has passed as well. Teams are bringing in prospects for personal workouts and formulating their draft boards. Of course, medicals play a huge part in their evaluations.
In honor of that, we are looking at 2018 NBA Draft prospects and trying to determine if we can glean anything about their future based on their respective injury red flags.
The draft is June 21.
For our analysis of Michael Porter Jr., click here.
For our analysis of Bruce Brown, click here.
For our analysis of Justin Jackson, click here.
As always, we’re not privy to specific medical information for these prospects; we’re just trying to draw conclusions based on available public information.
Today, we’ll look at dark horse first-rounder Kevin Hervey.
Kevin Hervey, Small Forward, UT Arlington Age- 21 Height-6’8” Weight-212 lbs
A small school prospect, Kevin Hervey did the heavy-lifting for a UT Arlington squad as a three-year starter and averaged more than 20 points as a senior. He appeals to NBA teams due to his defensive potential with an 8-11 standing reach, 7-4 wingspan, and his promise as a three-point shooter. In fact, The Ringer called him “the most intriguing player of the combine” and that a team could take a swing at him at the end of the first round.
However, there is a major red flag on Hervey’s resume and considering this is a sports injury blog, you probably have an idea of what it is. When he was a senior in high school, he tore his right ACL. Then, during his breakout sophomore campaign in college, he tore the ACL in his other knee.
There is some evidence that once you tear an ACL, there is a higher risk of tearing the ACL in the other knee, though this risk seems greater in women than in men. But it’s a moot point for Hervey; he’s already torn both.
The ACL is a knee ligament that provides stability by preventing forward movement of the tibia in relation to the femur and controlling rotation of the tibia. Basically, it controls pivoting movements. Most injuries are non-contact and are due to jumping, sudden deceleration, and pivoting.
Given that, it would seem that a player would lose a step or two athletically after tearing this ligament and that this change would be noticeable in some statistics, right?
Well, there has been a lot of research done in ACLs and NBA performance. Intriguingly, Kevin Pelton found that there was a decrease in efficiency upon return from torn ACLs—except most of the decline was due to scoring. Players tended to use less possessions and were not as efficient doing so. Meanwhile, “hustle” categories such as rebounding, blocks, and steals—categories that one would expect to be affected the most by decreased athleticism—either stayed the same or actually increased.
Similarly, Jeff Stotts at instreetclothes.com found that players tended to regress in PER (Player Efficiency Rating) the season following ACL surgery, though most of them experienced a rebound effect in the second season afterwards. Several of the admittedly small sample would go on to have career-highs in PERs in the years after surgery. There was also evidence that age played a factor: three-quarters of the players age-23 or younger at the time of injury would eventually have their career-best PER seasons after the surgery.
The thing to remember, however, is that Hervey is already two years out from his second ACL surgery. Therefore, according to the data above, he should be fully recovered, or very close to it, by now and that this should be reflected in his statistics. Let’s take a look:
Kevin Hervey Pre- and Post-ACL
|Leading up to ACL||1 season Post-ACL||2 seasons Post-ACL||Average Post-ACL|
TS% = True Shooting Percentage
TR% = Total Rebound Percentage
STL% = Steal Percentage
BLK% = Block Percentage
From this table, we see little drop-off. His PER massively improved, along with his shooting percentage; the rest of his “athletic” traits generally stayed the course. From this we can draw the conclusion that yes, he indeed is fully healed, or at least the ACL tear didn’t prevent him from shouldering a heavy load at an efficient level. In fact, thanks to hoop-math.com, we can look a bit closer and see that Hervey actually increased his percentage of shots at the rim in his years after the tear (23.3% in year one post-injury to 29.0% to year two). This suggests that he was even more confident in the stability of his knee as time went on as driving to the rim would involve cutting actions against defenders.
However, that was college. Now we’re talking about the NBA. Hervey won’t have plays called for him and he is unlikely to have the ball in his hands for stretches. He was barely an adequate three-point shooter in college; his best three-point percentage was 34.5% in his junior season (he actually regressed half a percentage point his senior year). However, his free throw percentage of 80% is a little more promising; using this Google Sheets calculator from this study investigating the relationship between free throw percentage and future three-point shooting, his projected NBA three-point percentage is about 37%, which is much more palatable. So you can understand why teams think he can contribute as a stretch player.
Another way he can contribute is his activity as an off-ball player. The Ringer mentions his ability to set screens, sprint in transition, and cut to the rim. He will likely have to rely on changing speeds quickly and making sudden movements to be effective.
To wit, a look at Hervey’s NBA combine numbers reveals that his Lane Agility Time of 11.28 seconds would rank among the bottom-third of small forwards this year (Hervey is listed as a power forward in the database and that time would be second among that group; even though that may be his eventual position in the NBA if teams see him as a stretch-four, the small forward group is a closer match physically). His Shuttle Run ranks average. Since we don’t have data for these drills during Hervey’s freshman year, we are unable to quantify any change in his agility after the ACL injury. However, as it currently stands, it does suggest that Hervey may have trouble chasing wings on defense and may be limited to more of a stretch-four role in the NBA. If a team views him as such, then perhaps there would be slightly less concern about the ACLs in a way as he would be more reliant on his shooting to provide value and a little less reliant on cutting given he would likely be able to stay in front of the more flat-footed power forwards.
Finally, NBA teams are likely concerned about both the longevity of his career and the possibility of re-injury. In order to determine teams’ behavior when presented with such a prospect, I looked at NBA prospects entering the draft from 1989 to 2007 who had a known history of at least one ACL tear. I chose 1989 as a start date as my internal NBA injury database starts there; I also feel this is a reasonable start point because the further you go back in the annals of NBA history, the harder it is to glean a player’s high school and college injury history from simple internet searches. I chose 2007 as an end date because I wanted to get a good feel on how total career arcs played out; as you are about to see, Baron Davis tops the list below at 835 games played, so I wanted to give players an opportunity to top that number. Eleven seasons have been played since the 2007 draft, which would give such a prospect a chance to top that number (any subsequent drafts would mean that we are artificially capping career games played); in addition, several players in the following drafts are still active. Finally, international players were excluded.
There is a chance some players have been accidentally omitted, especially since high school injury information is hazy; please let me know in the comments if I have missed anyone and I’ll incorporate them into the table.
NBA Players Drafted with Known History of ACL Tears At the Time 1989-2007
|29.7 (Average)||318 (Average)||12.6 (Average, Cisse was assigned a 0)|
GP = NBA games played (not including playoffs)
PER = Player Efficiency Rating
Recurrence = ACL tear in either knee during NBA career
A couple of the players above had a known history of at least two ACL tears, but since the sample size was so small, I thought it was prudent to lower the threshold to one tear. In addition, as this is a list of drafted players, it obviously excludes players that went undrafted. It would be fair to say that there may have been prospects whose injury histories completely scared teams off from drafting them. However, that’s fine, since right now we’re much more interested in the outcome of a player’s career when an NBA team decides they are worth investing a pick in.
So what conclusions can we draw from this table? Well, it seems that when NBA teams decide a player with a known history of an ACL tear is worth using a draft pick on, they value these players at late first-round value. In addition, these players end up playing just about four seasons worth of NBA basketball. This is the length of a rookie contract for a first round pick (with team options in years three and four picked up). This player is also just about a rotational-level player (PER for an average player is 15.0). Finally, this player is actually better than the median-type of player taken at this draft slot.
In other words, for a late first round pick, NBA teams seem to get a decent value.
(Of note, Harry Giles, who tore both ACLs in high school, was taken 20th overall last year, which is consistent with this late first valuation. Of course, the jury is still way out on his NBA career).
As far as recurrences, three of the players went on to have another ACL tear in their NBA careers. It’s hard to say right now whether this rate would differ significantly from a randomly selected group of sixteen NBA players.
It should be noted, however, that several of the players continued to have knee problems in some other fashion (either tendinitis or loose cartilage or meniscus injuries) during their careers. This is not too surprising as there is evidence that ACL tears cause an increased risk of osteoarthritis and joint breakdown.
If you’re looking for an actual physical comparison, the two best ones for Hervey seem to be Blanton and O’Bannon. Performance-wise, that does put a bit of a damper on things, but it’s unclear if that has anything to do with the ACL history and not simply basketball reasons, especially given the small sample size.
Level of Worry: Hervey had an impressive Combine, so much so that The Ringer is mentioning him as a possible late first round pick. If an NBA team decides he is worth investing a late first rounder in despite the injury record, history has shown that odds are good they will end up with a useful player; if anything, it has shown that collectively these players have actually out-performed the typical player taken in their average draft slot. Hervey has legitimate questions about his ability to contribute at the NBA level for basketball reasons; his ability to guard the perimeter is a gray-area and, if teams view him as a stretch-four, it is unclear if he can develop the big man skills to fully utilize that role. His history of multiple ACL tears, while lacking a sizable draft precedent, hasn’t appeared to hamper his game, likely in part due to his age; he proved his confidence in his knees’ stability by increasing the number of his drives to the rim as his college career went on and his production exploded as he shouldered a heavier workload. Since research has shown that the chances of developing arthritis in the knees within a decade of an ACL tear could be 50 percent, it is likely that Hervey will have knee trouble before he hits his 30s and that could start costing him games. So I am moderately concerned that he won’t have a very long career. However, if a contending team in the late first round feels that adding a rotation player for four years—and not much beyond that—is worth the pick, then I am only minimally concerned that Hervey’s ACL history will be what holds him back from fulfilling that role.
Thanks to Brukner and Khan’s Clinical Sports Medicine for providing information. Thanks to basketball-reference.com, hoop-math.com, ProSportsTransactions.com for additional statistical and injury information.