In their second game of the 2019-20 season, the defending champion Toronto Raptors played the division rival Boston Celtics. Boston had struggled offensively in its season opener, scoring only 91.4 points per 100 possessions in a loss to the Philadelphia 76ers, and once the game got underway, Toronto replicated much of Philly’s defensive strategy.
The Raptors did not send a single double-team on any of the Celtics’ 19 isolation plays, per Second Spectrum (the Sixers had doubled on zero of 20 isolations). They played soft coverage, with the big man hanging back, or ice coverage, with the on-ball defender forcing the ball-handler to the sideline or the baseline, on 59 of Boston’s 73 actionable pick and rolls, and they did not send an extra defender to blitz the ball-handler a single time (the Sixers played soft or ice coverage on 62 of 71 actionable pick and rolls and sent just one blitz). They were similarly passive against off-ball screens and dribble handoffs, sending zero blitzes on 62 such actions while playing soft or drop coverage 47 times (the Sixers played soft or drop on 48 of 72 off-ball screens and did not blitz at all). But the Raptors did not replicate the Sixers’ results. Jayson Tatum, Jaylen Brown, Kemba Walker and Gordon Hayward combined for 87 points while hitting 11 of 26 3-point attempts, Boston scored 110.7 points per 100 possessions, and the Raptors lost by 6.
About a month later, the Raptors had gotten more aggressive. Against the Dallas Mavericks, they blitzed Luka Dončić on 27 of his 34 pick and rolls — tied for the greatest number of times any player has been blitzed in a game this season. The Raptors succeeded in holding Dončić, as he shot only 5 of 14 from the field, but they also fouled him enough to send him to the line 19 times — and they ended up losing the game by 8.
Not long after that, the Raptors employed a game plan against the Houston Rockets so outlandish that, according to ESPN’s Zach Lowe, Second Spectrum doesn’t even have the capability to categorize it. Raptors coach Nick Nurse teased reporters the day before the game with hints of a mystery defense, and what he unveiled was pretty unusual indeed. Just about every time James Harden crossed half-court, the Raptors had Fred VanVleet come up and double-team him to get the ball out of Harden’s hands before any action could even start.
Harden had been on an absolute tear through the first 20 games of the season, racking up a completely ridiculous 39.5 points and 7.8 assists per game while taking 24.8 shots and 14.9 free throws. Averaging a league-high 19.3 isolations per contest coming in, Harden was practically impossible to stop: Any Houston trip including a Harden iso was producing 1.322 points per possession. That is the stuff of legends.
But Harden didn’t come close to replicating any of those figures against Toronto. He got only four chances to isolate, with those possessions creating a total of zero Rockets points. He ended the evening with just 23 points, three assists, 11 shots and six attempts from the charity stripe. Mission accomplished, right? Well, not so much. The attention the Raptors paid Harden meant they sprung massive leaks everywhere else in their defense. Harden’s teammates went 19 of 50 from beyond the arc, and the Rockets won the game.
After the game, Nurse called his gambit an “interesting experiment.”
VanVleet, for his part, went a bit further. “If we would’ve scored 11 more points, we’d be geniuses and the defense was the best in the world and we would’ve been Harden-stoppers,” he said. “But we lost and so it didn’t work and you go back to the drawing board.”
The Raptors live at the drawing board. Though their defensive experiments might occasionally end in losses, they exemplify what has made this year’s squad a serious threat to get back to the NBA Finals even after losing arguably the best player in the league in Kawhi Leonard. Because while the schemes themselves were outliers, the aggressiveness with which they were deployed and the wild swing between strategies were anything but.
Nurse’s Raptors are among the most aggressive defenses in the NBA — not just this season, but at any time in the past seven seasons. But how can we compare this defensive strategy to others in the league? We did it by building two new metrics: Aggression+ and Variance+.
Using Second Spectrum’s tracking data to identify which coverages teams play against five offensive actions — pick and rolls, isolations, post-ups, off-ball screens and dribble handoffs — we created Aggression+: an index statistic that shows how aggressive a team’s defense is relative to the average team in the league that season, both against every individual action and overall.
The league average is set at 100, and each point above or below indicates that team is 1 percentage point more or less aggressive than the average team in the league. Teams that blitz pick and rolls and dribble handoffs, double-team isolations and post-ups, and jam or switch off-ball screens are considered more aggressive, while those that drop their big man back into the paint on screens and rarely send help at one-on-one plays are considered less so.
The pre-hiatus Raptors employed the most aggressive post-up defense of any of the 210 team-defense seasons over the past seven years, doubling 12.4 percent more often than the average squad. They were similarly aggressive against isolations (14th), off-ball screens (fifth) and dribble handoffs (eighth). Only against pick and rolls were they outside of the top decile, ranking 48th out of those 210 team seasons. Taken together, the 2019-20 Raptors’ aggregate score is the 14th-most aggressive overall defense of the past seven seasons.
The Raptors are something of an outlier among the most aggressive units. Of the 15 most aggressive defenses of the past seven years, only two others ranked inside the top five in defensive efficiency during that season, per NBA Advanced Stats. On average, the non-Toronto teams ranked 17th in the league, indicating below-average overall units.
But employing that level of aggression is not the only thing that makes the Raptors defense unique. It’s that they are also among the most willing to alter their tactics.
Armed with a deep, versatile roster stocked with hyper-intelligent defenders, Nurse is the NBA’s most inventive defensive coach, tinkering night to night and even on the fly within games. He broke out both a box-and-one and triangle-and-two in last year’s NBA Finals against the Golden State Warriors. He’s willing to use zone defenses more often than most other coaches. He’ll double at half-court in one game, blitz every pick and roll in another and drop the big man nearly every time in the next.
Nurse can afford to get creative with Kyle Lowry, Serge Ibaka and Marc Gasol to anchor his schemes, plus an emerging wing stopper in OG Anunoby; a rangy, kinetic menace in Pascal Siakam; a feisty, do-whatever-is-necessary pest in VanVleet; and multi-positional reserves like Norman Powell, Rondae Hollis-Jefferson and even Terence Davis and Chris Boucher. With a group like that, Nurse can easily go big or small. He can aim to control the pace or to make things more hectic. He can play fast or slow, focus his defensive efforts inside or out. He can play man or zone or a hybrid of both and switch freely on any trip down the floor. He essentially uses the season as a long-running experiment, throwing defenses against the wall to find out what works and what doesn’t.
And this, too, shows up in the tracking data. By calculating the variance in each team’s Aggression+ for each play-type and overall in every game they played, we created Variance+: an index statistic that shows how often a team changes up its coverages on a night-to-night basis, both against every individual action and overall, relative to the average team in the league that season.
Again, the league average is set at 100, and each point above or below indicates a team is 1 percentage point more or less willing to vary defensive strategies than the average team. Teams like the Raptors that are willing to swing from one extreme to the other and hit every point in between have high Variance+ scores, while teams like the Orlando Magic, who almost always employ the same coverages every night, have very low scores.
Here is where the Raptors really stand out. First off, they are an outlier among this year’s top defenses. Of the top-10 point-prevention units in the NBA this season, six of them rank 189th or lower since 2013-14 in Variance+. The Raptors rank 12th, changing their schemes night-to-night 77 percent more often than the league-average team this season. The next-closest top-10 unit is the Lakers, who rank 99th.
And among the teams most willing to change schemes from game to game, the Raptors are again a bit of an outlier. Only one of the other top 15 teams in Variance+ in the past seven seasons sported a defense that ranked inside the top 10 during that season, per NBA Advanced Stats, while nine ranked in the bottom 10 (three were in the bottom five). On average, those 14 other teams had the 20th-best defense in the NBA that season.
That gets at a key contrast between this year’s Raptors and most of the other teams that shift defensive strategies from one night to the next: Those bad defenses are doing it because nothing works, and so they’re searching for anything that can help them get a stop. The Raptors do it as a proactive strategy, both to throw opponents off their game and because they can.
And the Raptors are not just willing to shift strategies based on that night’s opponent. They’ll junk their plan against a certain adversary and throw something completely different at them if whatever they did the first time around didn’t work. Again, almost all teams are willing to do this if necessary, but the degree to which the Raptors are stands out.
In their second matchup against the Mavericks, for example, the Raptors dialed things back considerably from the level of aggression they showed in that early-season contest. Conversely, the Raptors got more aggressive the second time they played the Portland Trail Blazers, as well as with each successive game they played against the Charlotte Hornets. There were several teams against whom Toronto’s strategy remained consistent, of course, but how much they were willing to swing between tactics even against repeat opponents is notable.
Inside the NBA bubble at Walt Disney World, the Raptors have seemingly been the one team able to consistently get stops. During the seeding games, Toronto led the league in defensive efficiency, and it wasn’t particularly close. Nurse and company remained unsurprisingly willing to vary their level of aggression within and outside of their base schemes from night to night, against every type of action and overall, with the starters and with the bench.
This, more than anything else, is the key to the team’s title defense. Toronto’s offense checks in just outside the top 10 for the full season, and it’s been dreadful during the restart. According to Cleaning the Glass, the Raptors rank a disappointing 15th in half-court points per non-garbage-time play on the year, but they minimize the impact of that ranking by playing in the half-court less often than any other team. Their defense is a large part of what fuels the transition attack, which helps make up for the poor performance against set defenses.
However you slice it, this year’s team does not have the elite, top-five offense last year’s had. They also don’t have the best defender from last year’s squad, nor one of its other top perimeter stoppers. But as they open their playoffs tonight against the Brooklyn Nets, the Raptors still have Nurse, plus Lowry, Gasol, Ibaka, Siakam, Anunoby and VanVleet. And they have the capability to play any defense they want on any given possession, on any given night. If they’re going to find a way to repeat their incredible run from 2019, that shapeshifting is what’s going to carry them across the finish line.
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