Re-evaluating how to evaluate big man defense in the draft

Defense is inherently important for success as a big in the NBA, but many big prospects struggle to make an impact there in college. How can we project who will be good defenders in the NBA, and how can these players provide value if they aren’t?

The 2018 NBA Draft class was an outlier year for big men in many ways. Five bigs went in the top seven picks — Deandre Ayton, Marvin Bagley, Jaren Jackson Jr., Mohamed Bamba, and Wendell Carter Jr. — an impressive counter to the league’s ever-growing small-ball frenzy. And the players deserved it. We’ve never seen quite a collection in this volume of physical tools, athleticism, and high-skill play at the college level. However, it was also an outlier because most of the focus was placed on the potential these bigs could have offensively — forgiving or ignoring that each had a defensive issue that could hinder their ability to add value in the NBA.

Deandre Ayton routinely missed rotations and didn’t finish plays. Bagley played 2-3 zone and didn’t seem to understand the basics of defensive positioning. Jackson fouled too much. Bamba didn’t look agile enough to defend in space. And Carter’s leaping ability and functional strength seemed to put a cap on his potential as a rim protector.

These issues had varying levels of concern, obviously. Jackson was a monster on defense in college and the fouling projected more as a sign of aggression than anything too serious. Carter looked like he might just be playing in a bad system for his skill set, and Bamba was still the best rim protector of all five even if he didn’t have the lateral quickness for the perimeter. Meanwhile, Ayton’s lack of play recognition and effort, and Bagley’s fundamental flaws, were major red flags for their long-term value. And through their rookie years, this has mostly played out as expected. Jackson has a high foul rate but it hasn’t stopped him from being a net positive on defense. Carter has thrived in NBA space where he’s asked to be used as a perimeter defender far more frequently. Bamba provides positive rim protection but can’t stay on the floor. And Ayton and Bagley, with their more fundamental flaws, are for the most part negatives for their team’s defense so far.

Big man defense has been under a microscope in recent years, as a new wave of high-profile big men has proliferated the league. Karl-Anthony Towns, Nikola Jokic, and DeMarcus Cousins, among others, have redefined what it means to provide offensive value at the five, and all three of those players in particular coupled that offensive brilliance with significant defensive limitations. Since defense continues to be the primary route to value for bigs, growth there is vital to get the most out of them, even with these significant gifts.

However, growth on defense can be a process, as we see at other positions. Big men are typically more well-refined by the time they get to the NBA because of how important their execution is to success at lower levels, but their growth still can take time as they adjust to the speed and timing of the game, or wait for their bodies to fully mature. That can make evaluating players who struggle on defense difficult to evaluate because those negative traits can conceivably be fixed with a focus on development, as the Kings saw with DeMarcus Cousins during his early career.

In the context of the draft, this can make it difficult to evaluate prospects who struggle on defense but have significant offensive gifts. On one hand, the offensive value is becoming more and more important as teams require multiple ball-handlers and scorers to thrive against modern defenses, and you can get away with playing players like Jokic with large usage in big minutes if you put a good roster around them, and relying on the incremental expected development can often yield good results for the players’ overall defensive outcome. But at the same time, if a player is starting far behind in fundamentals, athleticism, or awareness, it can be difficult to expect even the incremental jumps that allow them to eventually become at least passable.

The 2019 NBA Draft class features three players who make good test cases here — Bol Bol, Jaxson Hayes, and Simi Shittu. These players all flash excellent offensive potential at the five, with outlier skills that could certainly make a transformative impact on their offenses — Bol has his pull-up shooting and finishing, Hayes has vertical spacing, and Shittu has elite passing touch. They also have obvious NBA length and athleticism — Bol’s 7-foot-3 frame and 7-foot-8 scream rim protection, Hayes is nearly 7-foot and still might be growing, and Shittu has good lateral quickness and burst off the floor at a healthy 6-foot-10. But defensive limitations will likely be a constant theme early in their careers. Let’s explore how severe those limitations could be.

Physical limitations can often be the biggest impediment to a center providing value on defense, and the repair that can be done on these issues varies. A slow-footed big like Jokic will struggle to contain penetration on the perimeter, and while that can be improved with work on footwork or compensated for with innate anticipation of opponent movements, there’s always going to be a cap on how effective a less agile big is going to be as a pick-and-roll defender.

Leaping ability can also limit effectiveness as a rim protector, and really isn’t developable — hence the classic “above the rim” and “below the rim” designations. Meanwhile, strength and coordination, which are often the most important physical variables for big men, can and often do improve through the development cycle. While there are always outliers that never develop requisite strength due to a poor frame or poor development (Dragan Bender is a good example), most players get stronger and more coordinated as they mature and get used to the unnatural human task of “moving while being 7-feet tall.”

This is why being high on Bol’s ability to handle post-ups and contests at the rim isn’t crazy, despite his very thin frame. While there’s certainly the potential that Bol never gets strong enough to be a destructive defender, he still does have some room to add muscle to his skinny frame, and should reliably be expected to. That will be coupled with his wingspan and innate coordination, which will certainly help him affect shots at the rim, even if opponents can knock him off his spot.

It’s also why Jaxson Hayes’s difficulties with rebounding aren’t really a big deal, either. Yes, Hayes struggles to seal on box outs currently, so much so that upperclassmen opponents can physically drag him across the court:

But given that he is fresh off a monster growth spurt, is the most fluid athlete in the class, and has a great frame to add to, it would be foolish not to assume that Hayes is going to be able to achieve the requisite strength needed to make the best use of his talents.

Of course, this doesn’t mean strength isn’t a valuable projection piece. Strong players win out, especially on defense, and if a player has that requisite strength, it’s going to make life easier in the NBA, especially in the transition period. Steven Adams and Aron Baynes are always going to give guys like Rudy Gobert issues. Heck, one of the reasons John Collins surprised in his rookie season was the marked strength gains he made from his time at Wake Forest. It’s an important aspect of the physical package for a big man, but it’s also an area that big men hit at different points in their development curve, and a 19-year old draft prospect that doesn’t have ideal strength should be bet on to make up that gap, especially if they have other tools to compliment it.

Identifying physical tools that matter is important, but arguably more vital is the identification of positive mental traits. Modern defense for bigs arguably relies less on physical dominance than it ever has, and more on the skills you would attribute to a soccer keeper — the ability to read a possession developing, react to it, and to be able to anticipate the strengths and weaknesses of the rest of your team defense and plug holes if needed.

That creates a major inefficiency in using college and high school tape to project defense — the lower levels just aren’t at the same spot in terms of strategy. This makes sense – -college kids making decisions! What could go wrong! — but it means that we often don’t see college players in a context that actually tells us how that player will fit into the NBA. It’s also why the learning curve is so long for NBA defenders in general, even big men who look advanced in college — the systems are completely different, infinitely more complex, and let’s not forget that the strength and athleticism curve is entirely different, as well. In college, bigs are routinely defending post-ups, or standing at the rim guarding the dunker spot. Bol and Shittu spend a lot of time in zone. Depending on the scheme, you may never see a big that will be expected to defend on the perimeter regularly or never defend a pick-and-roll straight on in college.

Instead, you have to rely mostly on flashes of instincts and disruptive play that can translate to what big men need to be good at in the NBA. A positive sign is a college player who is constantly involved in defensive actions at the college level, like Jaren Jackson Jr. last season. Activity at the college level unveils instincts and a baseline of athleticism and aggression that is necessary for performance at the college level. Here is where Hayes shines. His positioning and feel on defense aren’t at the level that they’ll need to be in the NBA, but he instead impacts an absurd number of shots at the rim, and his recovery when he’s put in a bad spot is truly special.

Much like Jarrett Allen before him, Shaka Smart’s defensive system leaves Hayes glued to post players a lot of the time — but he still makes those quick rotations to contest that will be expectations at the next level. Simply put, Hayes doesn’t always put himself in ideal spots, but he finishes plays — and that’s probably more important.

Contrast that with Bol and Shittu, who are both cut from similar cloth in terms of the mental aspect of the game. Hayes is the outlier in the college game — more often, you see players like Bol, who flash dominant play and then turn around the next play and make you wonder how they could ever be drafted. Bol can have some truly brilliant displays of coordination, but he also struggles to pay attention to little details — like this play from the Iowa game, where he’s face-cut quite easily by his man.

He misses rotations regularly, doesn’t close out hard, and struggles to read the ball-handler when he’s switched onto the perimeter. Watching Bol neglect to contest when he’s the last man at the rim is incredibly disappointing, given how easy it is for him to actually affect shots when he makes the smallest rotation.

Shittu, meanwhile, makes Bol look like he has Clint Capela’s instincts at the rim.

The question around awareness is similar to the strength question — how much can we reasonably expect a player who has these lapses to grow during their early NBA career? Most players get better, to a degree, even outlier problem cases like Karl-Anthony Towns. However, few go from the level we see from Bol, Shittu, Ayton, and Bagley, and hit a consistent all-around defensive impact. However, there is an argument to be made that these players do have a shot at becoming positive rim protectors. Take the top five players in defensive field goal percentage allowed (minimum 5.0 attempts per game) each season since the stat was developed: Javale McGee, Hassan Whiteside (twice), Joel Embiid (three times), Myles Turner, Serge Ibaka (three times), Paul Millsap, Kristaps Porzingis (twice), Anthony Davis (twice), Jakob Poeltl, Draymond Green, Rudy Gobert (three times), Derrick Favors, Pau Gasol (twice), Brook and Robin Lopez (twice each), Timofey Mozgov, Alex Len, and Roy Hibbert.

There are several innately brilliant rim protectors on this list — the last two DPOYs in Green and Gobert, Embiid, and Ibaka, among others — but you’ll also see plenty of players who were at one point knocked for a lack of good decision-making and awareness. JaVale and Whiteside obviously stick out here thanks to their early careers, and while they may still be limited overall team defenders, they both have been able to grow into shot-blocking instincts and have positive impact at the rim. Brook Lopez improved his footwork and saw his instincts improve. Turner might be the best example here — he’s always had the athleticism, but in year four, is finally turning the corner in terms of understanding the little things great defenders do — not just protecting the rim, but bumping guys off screens, tagging the roll man, and generally making his presence felt.

This is why the dichotomy of projections of Bol’s defense is interesting to me — you’ll most often see Bol projected as either a dominant force at the rim, or completely written off into the Towns/Ayton tier of low-motor centers. The most likely outcome is probably something more in the Whiteside/Turner tier — a player who will give back points on some nights, but who with the right development and roster put around him, can be terrific as a rim protector.

It’s going to take Bol awhile to get there given where he’s starting at from a  motor perspective, but he did show good performance when Oregon ran zone. Confined to a smaller area of the court and a specific assignment, Bol seemed to make better and quicker rotations to contest shots. Given how much modern rim protection relies on zone principles, and that the prevalence of zone is increasing in the NBA, Bol becomes a lot more palatable if he isn’t having to switch on the perimeter or aggressively hedge pick-and-rolls. And remember, Bol’s offensive skill set is much more perimeter-oriented than most of the bigs we’re discussing here. He could be a brilliant fit on a roster like Atlanta, where he can function as a wing or four on offense, allowing the Hawks to pair him with Collins, whose aggressive energy on the glass and speed on the perimeter can let Bol hang back where his coordination and length will matter more.

This projection relies heavily on Bol’s inherent traits, though. It’s very hard to be a JaVale that doesn’t have a 7-foot-7 wingspan to erase delayed reactions and mistake, as we have seen from even Towns. That’s what makes Bol a viable defensive prospect, and Simi Shittu nonviable. Shittu has the same mistakes without the coordination and length that Bol has, and he even takes the misdiagnosis of plays and lack of effort to a higher level. Playing as Vanderbilt’s last line of defense, Shittu has just 12 blocks in 514 minutes. He projects to finish under 30 blocks in 800 minutes for the season. The only big to do that at the college level since 2010 is Adreian Payne – who famously got traded after half a season in Atlanta because he couldn’t grasp Mike Budenholzer’s defensive system. Guys with Shittu’s profile — good but not great size, average NBA athleticism, and little to no havoc creation — don’t just fail in the NBA — they often don’t even get a shot.

Evaluating big men is just as difficult as evaluating primary initiator guards. Many bigs can produce at the college level without having it matter at the NBA level, and raw big men can and do become productive as their bodies mature and they learn how to be rim protectors at the NBA level. They also bust at a similar rate, either because they lack a fundamental physical attribute or never get the mental aspect of defense down. It’s easy to get lost in a big man’s offensive potential — I certainly did in my early viewing of Shittu, hence this ranking — and neglect that their defensive value is going to be far more important at the NBA level. But it’s also easy to see a player like Hayes that gets tossed around by stronger players, or Bol who should be a dominant force but doesn’t try hard and write them off too.

In summary, the best way to project players like this is to weigh these major skill areas against each other and identify traits that a player can’t compensate for. Bol and Shittu have similar issues with awareness, but Bol is going to be able to overcome those issues in ways that Shittu isn’t thanks to his length. All three of Hayes, Bol, and Shittu are affected by physical limitations, but Hayes’s strength is significantly less of a problem than Bol’s given his frame and athleticism, and Bol not having strength is still less of a problem than Shittu’s disappearing vertical. Knowing what traits matter is key, but even more important is the ability to weigh problems against advantages, and get a sense of how growth in expected areas blend with the strengths you already see.