Why is the Boston Celtics Defense Suddenly So Good?

Almost a month ago, I wrote about the Celtics 40/20 pursuit — the race to win 40 games before losing 20, which has been proven to be a key indicator of a team’s potential to win a championship. Since 1980, only four teams have won a championship without reaching the 40-20 rule: the 1994–95 Houston Rockets, the 2003–04 Detroit Pistons, the 2005–06 Miami Heat, and the 2020–21 Milwaukee Bucks.

Everyone else won 40 games before losing 20.

At that point, the Celtics were 30-18, and they needed to go on a 10-1 run. At the time, I wrote:

A 10-1 run is asking a lot of a team that' now 7-6 over their last 13 games. On top of that, winning 10 of 11 has to cross over the All-Star break and into a Western Conference trip against some tough teams.

All they’ve done since then is go 7-1 with the league’s fifth-best net rating. And they're doing it with the two things that were their weaknesses coming into the season, defense and rebounding.

Their defensive rating in February is 104.3, second-best in the NBA. Their defensive rebounding percentage is 74.7%, best in the league. Those numbers were 19th and 26th respectively in November.

Month	Defensive Rating (League Rank)
November	116.5 (19)
December	113.3 (10)
January	111.9 (12)
February	104.3 (2)

Month	Defensive Reb% (League Rank)
November	67% (26)
December	68.3% (18)
January	71.7% (9)
February	74.7% (1)

What’s behind such a steady upward march?

Rebounding is a massive part of this. The Celtics defense was getting crushed under the weight of second chances and extended possessions, so it’s no surprise that these two stats correlate. I don’t think there's any chicken-and-egg scenario here. The Celtics are rebounding better, and that's making their defense better.

Jaylen Brown is a big reason why that's happening. He’s gone from 5.1 defensive rebounds per game in December to 8.1 in February. He’s been filling a void left by Jayson Tatum, who has been Boston’s best rebounder in recent years. Now, with a wing crashing the boards, the Celtic can limit those second chances and get out in transition.

But it’s not just Brown. In November, Neemias Queta led the Celtics by rebounding 21.1% of opponent misses. Brown and Jordan Walsh were next at 14.8%. This month, Neemias Queta is leading the team at 21.8%, Brown is second at 21.1%, Baylor Scheierman is at 21% even, Nikola Vucevic checks in at 20.4%, and Hugo Gonzalez is at 17.1%.

Not only has Brown stepped up, the new guy is getting on the glass, and the role players are making a monster impact.

“Any great team has great role definition,” Joe Mazzulla said after beating the Lakers. “In order for us to be great, we have to have those guys impacting the game at a high level, on the margins. And they do a great job of that, and they take pride in that. So it's the defense, it's the rebounding, it's sprinting to the corners, it's defending without fouling, it's offensive rebounds.”

Scheierman has been a revelation recently. He’s stepped into the starting lineup and played well above any expectations of him because he’s become an exceptional defender and rebounder. His defensive rebound percentage was 8.5% in November, so it’s increased by 12.6%. He was the primary defender against Luka Doncic on Sunday and Doncic shot 3-8 with one assist.

Gonzalez is prone to fouling and making some rookie mistakes, but he’s making the most of his time on the floor. When equalizing stats per 48 minutes, Gonzalez leads the team with 2.5 steals in February. He’s been a disruptive defender, and he's tied with Derrick White for defensive loose balls recovered this month, showing he’s hustling at all times.

Walsh is right there with Gonzalez on steals and he’s one of the team’s leaders in deflections. He’s been trusted all season as one of Boston’s best point-of-attack defenders, and he’s been great at poking the ball free and getting layups.

This all ties into the increased rebounding numbers. The Celtics can now trust Scheierman, Walsh, and Gonzalez to guard their yards, which means less help being sent their way. By staying home, the Celtics can box out more effectively, and grab a higher percentage of the available rebounds.

We know the Celtics will get incredible defense from Queta at the rim and Derrick White on the perimeter. Brown is a two-way player who will take on the biggest challenges when he needs to. Those are constants. Those things were true earlier in the season when the overall numbers weren’t great.

And while there has been improvement from those guys along the way, especially as the defensive concepts get hammered home a bit more and the rotation gets more solidified, it’s the other guys who are filling important gaps to make the Celtics a suddenly great defense.