Jaren Jackson Jr’s Historic Not-So-Historic Season
If the NBA season suddenly ended today, a much more plausible reality than we were aware of a few short years ago, there’s a good chance Jaren Jackson Jr. would take home Defensive Player of the Year. The fifth-year power forward/center has been a one-man shot blocking menace to would-be scorers and the anchor for the Memphis Grizzlies’ number-one-ranked defense.
It doesn’t take advanced stats to understand that Jaren Jackson Jr. is up to something special. He leads the league in blocks per game at 3.1 and is only the fourth player to average over 3.0 blocks a game since 2008-09. With the explosion in 3-point attempts, blocks have gone the way of the mid-range jumper. To put in perspective how special a 3.0+ blocks per game season is in the modern game, Dwight Howard, Rudy Gobert, and Anthony Davis have never hit that mark.
While blocks per game are a good proxy for defensive impact, players who hunt blocks can find themselves atop the leaderboard even if their defensive impact is substandard. In 2015-16, Hassan Whiteside paced the league with 3.68 blocks per game, the best figure since 2000-01, but the Heat actually saw their defensive rating improve by 1.5 points per 100 possessions with him off the court. However, the Grizzlies’ defense is as reliant on Jaren Jackson as the Jackson Five were on Michael Jackson.
The Grizzlies’ 110.3 defensive rating paces the league, although the Cleveland Cavaliers and Bucks are fractions behind them, and their razor-thin edge in defensive rating is courtesy of the Lord protector of the rim (I’m trying here!)-- Jaren Jackson Jr. With Jackson on the court, the Grizzlies go from an average defense, (114.08 defensive rating) to an absolute elite unit (107.32 defensive rating).
The recipe for the Grizzlies is simple. Have Jaren Jackson anchor the stingiest defense within three feet. For the season, the Grizzlies’ opponents are shooting 64.8% zero to three feet from the basket, by far the best figure in the league and a massive 5.4% better than the league average, and things get even better with Jackson on the court. According to PBPStats, teams are shooting 56% at the rim with Jackson patrolling the paint, compared to 66% with him on the bench. (What PBP classifies as at the rim differs from Basketball Reference’s classification of shots 0-3 feet from the rim)
No matter how you slice it, Jackson is one of the NBA’s elite defenders and would be a deserving recipient of the Defensive Player of the Year award. He’s the most important defensive player on the league’s best defense. But that doesn’t really interest me all that much. What I do find interesting, and more worthy of celebration than a silly award, is that Jackson is in the midst of a historic shot blocking season, even if his blocks per game would look pedestrian in the block happy era known as 20th-century basketball.
Since blocks were first recorded in 1973-74, only Manute Bol has posted a single-season block percentage higher than Jaren Jackson Jr’s 9.97%. When I first started researching this article, Jackson was above 10%, no one but Bol has ever eclipsed 10%, and he did so in 1985-86, 86-87, and 88-89, but has slipped over his past two games. It’s unlikely that Jackson will surpass one of Bol’s seasons and move into the top three, but having the best non-Bol season should still be considered historic.
Bol was an extreme specialist and played significantly fewer minutes per game than Jackson is playing this season. When all you do is block shots and play sparingly, your rate metrics can start to get silly. However, this is where things take a surprising turn. Yes, Jackson is having a historic season, but his block percentage is also a bit of a mirage.
Blocks per game have generally been trending down, and the culprit is pretty obvious. As teams take more and more 3-pointers blocks go down. Because, unsurprisingly, 3-pointers are rarely blocked. This season, the Toronto Raptors lead the NBA in blocked 3-pointers at 39, while the Sacramento Kings are dead last with 4. Entire teams, who have five players on the court for every minute, never miss games for load management and are in an era of extreme 3-point volume and efficiency, can only muster between a blocked 3-pointer every other game and basically never.
However, the nerds behind block percentage are no dummies. They know threes are hardly ever blocked, and because of that, they’re removed from the equation. So while blocks are in decline, block percentage is actually on the rise.
(1000 is 10.00%, 750 is 7.50%, and so on)
When I began investigating Jaren Jackson Jr’s block percentage in a historical context, I assumed his near 10% block percentage would stand out as a massive historical outlier compared to the overall league environment. I wrongly assumed that the decline in blocks outpaced the decline in 2-pointers, but the opposite is actually true.
Not only are teams taking more 3-pointers, but they’re also taking more blockable 2-pointers. As NBA offenses have gravitated away from mid-range jumpers and prioritized 2-point shots closer to the basket, they’ve inadvertently created an environment that will juice block percentage. The 2-point shot diet of the NBA is being condensed and refined to contain more blockable shots, which has spurred the uptick.
Once I realized that Jaren Jackson was having a great shot blocking season but not a historic one, my attention immediately turned to Manute Bol. I used a simple trick to measure who was blocking shots at the highest rate compared to the league-wide environment. I took player X’s block percentage and divided it by the league average block percentage and then multiplied it by 100 to create block percentage plus (BLK%+). A score of 100 is league average, 101 is 1% above league average, and so on.
The best shot blocking season by this methodology was Manute Bol’s 1985-86 season, where his 10.62% block percentage (the NBA single-season record) led to an unfathomable BLK%+ of 172.4. For comparison, Jaren Jackson’s current season block percentage of 9.97%, the fourth highest ever, only registers a BLK%+ of 115.9. To match Bol’s 1985-86 season, he would need to register a block percentage of 14.8%. Simply put, Manute Bol is the block percentage and BLK%+ king.
Enough about Manute Bol, this is supposed to be about Jaren Jackson Jr, and his season, while not historic in a BLK%+ context, is still an excellent season. His BLK%+ of 115.9 is the best since Hassan Whiteside’s 118.7 in 2015-16, and only seven other players have ever had a single season BLK%+ eclipse 115; Serge Ibaka, Alonzo Mourning, Shawn Bradley, Manute Bol, Mark Eaton, Tree Rollins, and George Johnson.
Jaren Jackson Jr. should win Defensive Player of the Year and solidify himself as the great shot blocker of his generation. While he’s unlikely to ever stand out as much as Manute Bol or Mark Eaton in BLK%+, he can take solace in the fact that he’s capable of contributing on the offensive end and is a far better player than either. Jaren Jackson Jr. is having a historic, but not quite as historic season as I had hoped, season.
A special thanks to James Piercey, Above the Break’s better half, for help editing this piece.
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