How the Boston Celtics Became the NBA’s Top Defensive Team

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After playing a game across the pond in London against the Philadelphia 76ers, the Boston Celtics are now a couple games past the halfway mark of the NBA regular season. They currently have the best record in the East at 34-10, along with the second best overall record in the NBA.

Many different people can claim credit for this surge back to the top of the East; Danny Ainge for grabbing the necessary pieces to build a deep and concrete roster, Brad Stevens for continually proving that coaching really does matter in the NBA and showing that he can get the very best from almost any player that is put on his roster, or to each of the individual players on the team that give it their all each and every night.

There is little surprise in the team’s overall offensive productivity. The addition of perennial All-Star Kyrie Irving has helped along the development of young talent like Jaylen Brown and Jayson Tatum. The sudden burst of playmaking ability from guys like Marcus Smart and Terry Rozier could also have been predicted.

However, where the Celtics have turned many heads this season is on the defensive side of the ball.

As it currently stands, the Celtics are holding opponents to 97.7 points per game, which is No. 1 in the NBA, giving them the ability to claim best defensive team in the league status.

The team’s ability to play better defense than offense on some nights is staggering. Coming into the 2017-18 season, no one expected them to play better on the defensive side of the ball than they did last year. Many even thought that they may see a slight decline defensively after the departure of elite wing defenders like Avery Bradley and Jae Crowder.

So, the question to be answered after hearing this: How is that possible?

Let’s take a look at the numbers so we can dissect this astounding feat:

DEFENSIVE EFFICIENCY

Defensive efficiency, also known as defensive rating (the projected amount of points a player will give up per 100 possessions), is the one statistic to show how well a player plays on the defensive side of the ball as an individual. If you take a look at this screenshot from Fox Sports, it shows you that the Celtics have four players that are top-10 in the NBA in terms of defensive efficiency (Aron Baynes, Terry Rozier, Jayson Tatum and Al Horford) while also having an additional three players in the top-25 (Jaylen Brown, Marcus Smart and Kyrie Irving):

https://www.foxsports.com/nba/stats?season=2017&category=ADVANCED&group=1&sort=5&time=0&pos=0&team=0&qual=1&sortOrder=0&opp=0

When seeing that the Celtics have seven of the top-25 players in the NBA in terms of defensive efficiency, and you also take into consideration that no other team in the league has more than three players in the top-25 (Philadelphia has Joel Embiid, Ben Simmons and Robert Covington, Oklahoma City has Russell Westbrook, Paul George and Andre Roberson) it makes plenty of sense how the Celtics rank as the NBA’s best defensive team.

Even though defensive efficiency is a larger overall statistic that takes some of the other specific statistics (steals, rebounds, etc.) into account, it’s important to look into the smaller factors as well so we can understand how and why the Celtics became this defensive juggernaut.

The statistical analysis could stop right here, but what’s the fun in that? Let’s keep going.

STEALS

What better way to prevent your opponent from scoring points on offense than to take the ball right out of their hands. Or as basketball-savvy people like to call it: steals. According to TeamRankings.com, the Celtics are fifth in the NBA in steals per game and third in the NBA in percent-chance that they will get a steal per-play:

https://www.teamrankings.com/nba/team/boston-celtics/stats

To break this down a little more, there are five different players on the Celtics that are averaging at least one steal per game. The Houston Rockets are the only other team in the NBA with five players averaging that many.

https://www.basketball-reference.com/teams/BOS/2018.html

It’s a very simple concept, but often gets overlooked: your defensive ratings will look much better if you are taking the ball away from the other team and not allowing them to score points on offense. If they don’t have the ball, they cannot score.

REBOUNDING

During the 2016-17 season the Celtics were one of the worst rebounding teams in the NBA. Going into the 2017-18 season, like I mentioned earlier, many thought that the team would be just the same if not worse in that category. However, adding players like Marcus Morris, Baynes and Daniel Theis has given the team a significant boost. They’re now getting sneaky good rebounding contributions from guys like Irving, Rozier, Brown and Tatum on any given night.

The Celtics rank top-10 in the league in terms of defensive rebounds per game and defensive rebounding percentage (courtesy of TeamRankings.com):

https://www.teamrankings.com/nba/team/boston-celtics/stats

Based off of general power rankings, Boston is one of two teams in the top 10 of the league that employs four players averaging at least 4.5 rebounds per-game, the other team once again being the Rockets:

https://www.basketball-reference.com/teams/BOS/2018.html

There are only two other teams in the league that have that many players averaging that many rebounds: the Sixers and the Indiana Pacers.

Even though we could look at other numbers such as blocks or field goal percentage to explain the Celtics defensive dominance, those numbers do not directly correlate to a change in possession, meaning the team shooting the ball still has an opportunity to score a basket after missing a shot whether it be because of poor shooting or a blocked attempt.

It will be interesting to see if Boston’s defensive tempo can hold up for the remaining 38 games on the schedule. Stevens and this Celtics squad have awed those watching with their aggression and energy on the defensive side of the court up until this point, so let’s see if they can keep it up.

Follow Devon Clements on Twitter @CLNSDev for more news and info regarding the Boston Celtics.