Deandre Ayton is probably going to be the no. 1 pick in next week’s NBA draft. Ayton certainly thinks so. The betting market thinks so. The Ringer’s draft experts think so, even though they also think Slovenian wing Luka Doncic is a better prospect.

The Ringer’s 2018 NBA Draft Guide Check out The Ringer’s analysis of the 2018 NBA draft’s best prospects

One need only examine Ayton’s body and body of work to see why that outcome would be preordained. The 7-foot, 243-pound center is built like a right-handed David Robinson, and he won Pac-12 Player of the Year in his lone college season at Arizona after averaging 20.1 points and 11.6 rebounds per game. He ranked second among all Division I players in player efficiency rating and produced the best PER for a power-conference freshman since Anthony Davis in 2011-12.

But while Ayton could probably average a double-double in the NBA tomorrow, his defense is less of a sure thing. To quote Kevin O’Connor from our NBA Draft Guide, one of Ayton’s weaknesses is that his “low block and steal rates are notable considering his elite measurables and theoretical defensive potential.” The question, then, for both the Suns’ front office and NBA observers at large, is how notable—should Ayton’s middling defensive metrics in college be real reasons for concern about his potential two-way stardom? And more broadly, what does that relationship mean for other big men under consideration at the top of the draft, where potentially four of the top five picks could be centers?

Ayton’s troubles indeed begin with his block and steal numbers, as both rates in college carry tremendous predictive power for a given big man’s NBA numbers. Since 2004—which is as far back as KenPom tracks individual player statistics—there have been 44 players picked in the lottery who fit two criteria: First, they are categorized by Basketball-Reference as either pure centers or forward/center hybrids; second, they played in college, rather than coming to the NBA from Europe or high school. For those 44 players, the correlation between block rates in their final college season and NBA careers is a robust 0.74, on a scale in which 0 reflects no relationship and 1 a perfect link. Steal percentage translates well to the NBA, too, with a 0.70 correlation for this group.

While blocks and steals aren’t the only marks of a solid defender, they are, at their simplest, measures of defensive activity. It’s possible to be a defensive asset without amassing these box-score tallies, but that manner of thinking doesn’t extend far; this isn’t football, where an All-Pro cornerback might not record interceptions because opposing quarterbacks just ignore his side of the field. Last season’s block percentage leaderboard in the NBA generally doubled as a rundown of the league’s top defensive big men; among players who started at least half their team’s games, the top seven were Kristaps Porzingis, Rudy Gobert, Hassan Whiteside, Clint Capela, Myles Turner, Anthony Davis, and Joel Embiid. Gobert, Davis, and Embiid are the three finalists for this year’s Defensive Player of the Year award.

Especially in the modern NBA, and especially for big men, who often serve as the only rim protection in four-out lineups, an absence of blocks is worrisome because a useful defender should collect them as a matter of course as he makes his rotations and interferes in the right place at the right time. Here’s Davis kick-starting a fast break by throttling a Steph Curry floater.

Anthony Davis with the block on Steph Curry. pic.twitter.com/YS1xNw6eIW — RealGM (@RealGM) May 2, 2018

That’s just a casual block from Davis, maybe the NBA’s most dynamic rejection artist in 2018. His defensive highlights feature a diverse set of swatting skills—with either hand, without regard for the position of his victims, at times subtly redirecting shots and, at others, smashing them like Kerri Walsh on a beach in London. It would be foolish to expect a 19-year-old Ayton to approximate an in-his-prime Davis, but Ayton falls well below even the college version, who admittedly still holds a high bar: Davis’s freshman block total more than doubled Ayton’s.

The strong link between college and NBA rates bodes poorly for Ayton, who has the physical skills to become an impact defender but not, thus far, the statistical acumen. Last season, the Arizona freshman blocked 6.1 percent of opposing 2-point shots when he was on the floor. That’s a non-negligible percentage, but it wasn’t anything special, either: Per KenPom, he ranked outside the top 100 nationally among qualifying players and just eighth in the Pac-12.

Ayton’s defensive numbers look even worse in comparison to his lottery contemporaries. Add to the 44-person group of big men picked in the past 14 lotteries the six bigs who might go in this year’s, and a round sample of 50 touted big men forms. Ayton ranks just 36th among that group in block rate (based on each player’s final college season), and in a tie for just 44th in steal rate.

Let’s focus mostly on the blocks issue (steals are important indicators, too, but they’re relatively rarer than blocks for big men). Here is every player in the 50-person sample with a worse final-college-season block rate than Ayton, along with his career PER in the NBA—a catch-all statistic in which 15 represents the league average.

Lottery Big Men With a Worse Final-College-Season Block Rate Than Deandre Ayton Player NCAA Block % NBA PER Player NCAA Block % NBA PER Jordan Hill 5.6 16.3 Kelly Olynyk 5.1 16.2 Bam Adebayo 4.9 15.7 Greg Monroe 4.9 20.2 Jakob Poeltl 4.8 15.9 Frank Kaminsky 4.5 13.3 Jahlil Okafor 4.5 16.0 Cody Zeller 4.4 15.2 Kris Humphries 3.6 15.4 Rafael Araujo 3.2 6.3 Domantas Sabonis 2.7 12.5 Marvin Bagley III 2.6 ??? Julius Randle 2.6 16.6 Lauri Markkanen 1.8 15.6

Araujo aside, none of these players is bad, but they were also all lottery picks, which means they entered the league with higher expectations. Monroe is the best of the bunch, and he’s a defensive sieve who has never started a playoff game. Not a single member of the group has made an All-Star team or received All-NBA or All-Defensive Team honors.

Limiting that chart to players who were worse than Ayton in college block percentage is somewhat unfair because it doesn’t include everyone in his vicinity; for instance, Al Horford (6.7 percent) and Andrew Bogut (6.2) both became plus defenders after finishing just slightly better than Ayton at college rejections. But Horford is a master of movement and spacing, and therefore doesn’t necessarily work as a replicable model for Ayton—see: his performance against Buffalo in Arizona’s NCAA tournament loss—and Bogut wasn’t able to harness his eventual NBA blocking ability until his fifth professional season. Ayton would be on his second contract at that point.

Ayton has a better defensive body than anyone else on that chart, which both helps explain why he might be able to exceed those comps’ NBA careers and raises the question of why, exactly, he struggled so immensely on defense in college. Was it an issue with effort? An arduous adjustment to tougher competition? Imprecise coaching? (Probably not the last one—Sean Miller’s Arizona team ranked 27th nationally in defensive efficiency in 2016-17, then 83rd in 2017-18 despite exchanging Lauri Markkanen for Ayton in the rotation and making few changes elsewhere.) Not knowing the right answer could cost Phoenix dearly.

Prodigious physical talents are no guarantee of staunch defense, after all. Look at one of Ayton’s comps, Karl-Anthony Towns, who is almost as athletic and just as naturally talented as Ayton, and who took until his third NBA season to start fulfilling his two-way hype. Ayton will be starting from a much lower baseline than Towns, too, making his learning curve against the league’s elite athletes and complex offensive systems even steeper; for now, he compares unfavorably to all college big men picked first overall since 2004.

College Big Men Picked No. 1 Since 2004 Player Year NCAA Block % NCAA Steal % Player Year NCAA Block % NCAA Steal % Anthony Davis 2012 13.8 2.5 Greg Oden 2007 12.7 1.2 Karl-Anthony Towns 2015 11.5 1.4 Andrew Bogut 2005 6.2 1.8 Deandre Ayton 2018 6.1 1.0

Ayton did excel in one defensive area in college: rebounding, as he grabbed 28.2 percent of opposing misses when he was on the floor, which places him in a tie for third-best in the 50-person sample. And besides Mo Bamba, who tied his 28.2 percent this season, the players joining Ayton near the top of that leaderboard were all small-conference bullies: Bogut (Utah), Araujo (BYU), Sabonis (Gonzaga), and Jason Thompson (Rider). But unlike block and steal rates, rebounding doesn’t translate particularly well between college and the NBA. For the 44 bigs who have played at both levels, the correlation for defensive rebounding rate is just 0.29, which suggests a far weaker carryover effect than for blocks and steals. Andre Drummond has the second-worst college defensive rebounding rate in the 50-player sample; he’s now the most prolific rebounder in the NBA.

If the Suns draft Ayton, they won’t be the only team in the lottery gambling on a defensive cipher. Whomever selects Marvin Bagley III will be offering a similar shrug toward college defensive statistics, as the Duke freshman posted even worse numbers than Ayton. Heck, forget Ayton—North Carolina forward Luke Maye had a better block rate than Bagley last season.

In the 50-player sample of lottery bigs, Bagley places in a tie for 48th in final-college-season block rate (2.6 percent)—which brings him even with Julius Randle and ahead of only Markkanen, neither of whom is a true center. Bagley’s presence in a zone defense might have lessened his block opportunities, but there’s a reason Duke coach Mike Krzyzewski felt uncomfortable asking his players—including, and perhaps chiefly, Bagley—to execute a more complex defensive system.

Those numbers suggest that Bagley might be better as a 4 than a 5 in the NBA. So do his measurements. Although he fits just fine alongside his draft compatriots in height, all of their wingspans outreach his by at least 4 inches.

2018 Lottery Candidate Bigs Player Height Wingspan Player Height Wingspan Mo Bamba 7'0.75" 7'10" Jaren Jackson Jr. 6'11.25" 7'5.25" Deandre Ayton 7'0" 7'5" Robert Williams 6'9" 7'5" Wendell Carter Jr. 6'10" 7'4.5" Marvin Bagley III 6'11" 7'0.5"

If Bagley is to shift down a position in the NBA, he will need to evolve into a perimeter threat on offense, as he will most likely share the court with a taller—or, at least, equally as tall and better at defense—teammate. Bagley did shoot 39.7 percent on 58 3-point attempts last season, but his unimpressive 62.7 percent free throw effort is likely more indicative of his true shooting talent. If he can’t defend like a 5 or shoot like a 4, where does Bagley fit in a modern NBA lineup?

Bagley’s inverse in this year’s draft is a player who seems like a perfect fit in a modern NBA lineup. Unsurprisingly, Davis in his omnipotent season at Kentucky tops the college block rate leaderboard with a 13.8 percent mark. Or, Davis topped the leaderboard, past tense, because he’s been usurped by Jaren Jackson Jr. The Michigan State big produced an astounding 14.3 percent block rate—that’s more than twice as high as Ayton’s, and 5.5 times as high as Bagley’s—in his lone season in East Lansing. A lofty college block total doesn’t assure Jackson of a successful NBA career, as Hasheem Thabeet (11.9 percent in college) can attest, but it’s a strong indicator that he can anchor a defense.

That block rate came with Jackson playing largely at the 4 in college, too, which separates him further from the likes of Bagley, who played next to fellow 2018 lottery candidate Wendell Carter Jr. in the frontcourt, and Ayton, who also started next to another center (fellow 7-footer Dusan Ristic). It’s easy to attribute the defensive underperformance of those two heralded freshmen to their position, but internal competition didn’t prevent Towns and Willie Cauley-Stein from collecting blocks at Kentucky, and just last season, Jackson proved that a top defender can cast his shadow over the full court regardless of role.

Jackson breaks further from Bagley when folding in his shooting numbers. His college free throw percentage (79.7 percent) is fifth-best out of the 50-person sample, and the four players above him—Myles Turner, Markkanen, Channing Frye, and Towns—all developed at least a decent 3-point shot. It’s not inconceivable that Jackson will be the best player from this draft: a true stretch 5 who can guard every position, protect the rim, and atone for teammates’ defensive mistakes. He minimizes space on defense while maximizing it on offense.

That combination is the dream inspired by the fourth notable freshman big in this draft class, Texas’s Mo Bamba. Although he doesn’t quite displace the Brow at the top of the block leaderboard, Bamba’s defensive numbers are almost as impressive as Jackson’s. A mature and fully actualized version of Bamba is Gobert with a jump shot, and in college, he fit at least the former part of that combination, with a 13.2 percent block rate that ties him with Nerlens Noel for third place in the 50-person sample of lottery bigs. His immense wingspan and reputation washes over even his fellow draftees; as Ayton told our Jonathan Tjarks in 2017, “I have to be like Mo Bamba. He swats everything.”

Mo Bamba's reach is dumb. He will block anything. pic.twitter.com/6TJulo5Ctk — Nick Neppach (@NickNeppach) February 1, 2018

The problem isn’t that Ayton wasn’t swatting everything; it’s that he wasn’t swatting much of anything. This isn’t to say that Ayton won’t ever become an All-NBA center or that he won’t help round out Phoenix’s young core, but Doncic’s flaws have been picked apart for a month while Ayton has slipped cleanly through to the head of the class. The recent history of college big men moving to the NBA with Ayton’s defensive line isn’t encouraging, and in a draft loaded with talent, there’s enough of a question that he shouldn’t be considered a slam-dunk top pick. He completes plenty of slam dunks, after all—he just gives up plenty, too.