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Ramon Sessions: The Curious Crusade in Peeling Back Raw Defense Numbers
Traditional statistics tell us new Knickerbocker Ramon Sessions does not do well on defense. When you look at advanced numbers and the “eye test,” a whole different story is told.
Evaluating individual defense is a difficult thing to do, even in the advanced statistics era of today. There are obvious displays of good defense and obvious displays of bad defense. We remember when a player strips the basketball from a driving guard, or when somebody completely misses an assignment and it leads to a wide-open three; those plays stick out in our minds and sometimes that’s all we need to label a player as a plus defender or a defensive liability.
But possession-to-possession, game-to-game, a player develops habits, and those habits define a consistency that make them into the type of overall defender we can more confidently classify.
The most recent free agent signing for the New York Knicks is point guard Ramon Sessions, who is a tricky player to evaluate. He is a player that requires analysts to consider a wide variety of information, from the general eye test to statistics to in-depth video review.
By traditional statistics, or advanced metrics derived from traditional box score numbers, Sessions rates as a terrible defender.
While we will show later why last season might have been Sessions best defensive performance, Defensive Box score Plus Minus (DBPM) disagrees. Last season, his DBPM of -2.2 ranked 17th lowest among the 19 Charlotte Hornet players who suited up for at least one minute. Over the past three seasons, his combined DBPM of -1.7 ranks 232nd of 272 players who played at least 150 games. Not good.
But if we dive deeper into the statistic, we can understand why Sessions has such a low DBPM. In fact, Klay Thompson, who has turned into an elite defender, ranked even lower than Sessions in DBPM over the past three seasons. Why? Because DBPM is, as the name implies, a box score derived metric. If a player doesn’t accumulate a lot of blocks or steals, their DBPM is impacted: Over the past three seasons, of the 272 players who played at least 150 games, Sessions ranked 161st and 269th in steal percentage and block percentage, respectively.
DBPM is not good at evaluating how well a player closed out on a shooter or navigated around a tricky screen. It is a statistic that uses box score stats, mostly offense-based, to derive a defensive approximation. Defensive BPM is simply overall BPM minus offensive BPM.
To get a better idea of a player’s defense, we have Synergy data. Synergy uses real-time video-indexing to capture player movements and classifies the outcome of plays based on the offensive play type and defensive position. From this technology, we know how often Ramon Sessions was the primary defender in pick-and-roll or against spot-up jump shots, and how often opposing teams scored on those plays. This is where the analysis of Sessions’ defense gets complicated. The Synergy data shows a stark improvement in his defense last year.
As expected for a point guard, Sessions finds himself most frequently defending pick-and-rolls and spot-ups. Isolation numbers should be taken lightly as he only defended 10–20 isolation plays per year in the years highlighted above. But overall, at least by the outcome of plays he defended, Sessions could be classified as a stellar defender last season in Charlotte.
It’s too bad that Synergy does not take into account quality of competition. Remember, Sessions has mainly been a bench player in the NBA. He played behind Kemba Walker last season, who played a lot of minutes. (In fact, Walker was 13th in the league in minutes played, totaling 2739.) Perhaps the amount of points allowed per possession with Sessions as a defender is a byproduct of matching up against bench players.
Which brings us to the “eye test.” After watching hundreds of clips of Sessions on defense, there are real signs of improvement on defense, but he is still susceptible to error, and his gaffes, the ones fans remember, are really bad.
If Sessions is expected to play against starters next season, as Frank Ntilikina develops, the Knicks will likely suffer defensively. Sessions is best suited in limited minutes against starters, so he can focus his play, and matching up the rest of the time with opposing bench players, where poor shooting to make up for the occasional (on a good season) missed assignment.
Sessions biggest challenge seems to be grasping team defensive concepts, perhaps a product of him jumping around the league. He struggles the most staying in coverage off the ball, often losing his man, and then sort of floating around in no-man’s land. He has drastically improved this part of his game, which is what has turned him into a better defender. But the forgetful moments always return.
The concern for Knicks fans should be whether or not Sessions falls back into bad habits on a consistent basis now that he will be playing on a team not known for their team defense. And with a younger core moving forward, the Knicks Kids need to solidify their team defense, hopefully something Sessions can contribute.
— Jeffrey Bellone, columnist
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