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How the Celtics have transformed into the NBA’s best defense

Breaking down the factors that make Boston’s defense tick

San Antonio Spurs v Boston Celtics Photo by Brian Babineau/NBAE via Getty Images

It’s no secret that defense has been the key to the Boston Celtics’ recent success. Since the calendar turned to 2022, Boston ranks first in defensive rating (103.4), first in opponent’s points per game (100.6), and first in opponent’s field goal percentage (42.0 percent). They’ve even managed to overtake the Golden State Warriors, claiming the best defensive rating for the entire season.

In that time span, the Celtics have gone 23-8, climbed to fourth in the Eastern Conference, and helped Ime Udoka take home his first Coach of the Month award. But what is it that makes the defense so special?

Well, in short, there are a lot of things to point to. So instead of trying to lump it all into one big reason, let’s do a rapid-fire breakdown of some of the best features of Boston’s defensive scheme

1. Free safety Robert Williams

This is likely the most talked-about factor in what has made the Celtics so effective on the defensive end. For the first few years of his career, Robert Williams was tasked with guarding opposing centers. But now, Udoka is using him as an off-ball helper who can shut down drives and cuts in the blink of an eye.

While the usual outcome is a block by Williams, his great defensive IQ allows him to nab steals, too, as seen in the play above. (Also, shoutout to Jayson Tatum for the hustle play that made that steal possible.)

And when teams try to attack Williams in the corner with smaller wings, he uses his insane athleticism and quickness to shut that down, too.

Boston prefers to have Williams in the corner at all times, and it’s caused nightmares for opponents. His shot-blocking abilities were always there, but he’d often end up fouling out whilst banging down low with opposing bigs. But putting him in this position has allowed Williams to thrive, and in turn, Boston’s defense has improved tenfold.

2. Switch everything

At the start of the season, fans and media were criticizing Udoka’s “switch everything” style of defense. On Opening Night against the New York Knicks, Williams guarded Derrick Rose and Boston’s guards were constantly matched up with Mitchell Robinson. But fast forward to now, and that same switch everything style of defense is working wonders.

The reason behind it? Everybody on the floor can guard every position. Sure, having Al Horford matched up with an opposing point guard isn’t ideal, but for a possession or two on a switch, he can hold his own. There’s no defensive weak point in the Celtics’ starting lineup. And even taking a look at the bench, Udoka’s two top guys - Derrick White and Grant Williams - are both plus defenders.

Brad Stevens’ has hand-picked a roster that fits in perfectly with what Udoka wants to do on the defensive side of the ball. It may not have worked from the jump, but now that the team has gotten in a rhythm, they are absolutely dominant. Instead of allowing opponents to get a step ahead off of screens and hand-offs, Boston simply switches, thus giving the offense no room to work. Here are a couple of prime examples of the defensive scheme working its magic.

Look at the beautiful defensive movement!

That example was too good to leave out.

3. Marcus Smart being Marcus Smart

It’s hard to have a great defensive team without an elite defender leading the charge. The Warriors have Draymond Green, the Utah Jazz have Rudy Gobert, and the Cleveland Cavaliers have their frontcourt pairing of Jarrett Allen and Evan Mobley. It’s rare for that defensive leader to be a guard, but that’s exactly what the Celtics have.

Marcus Smart has been known for his great defense throughout his entire career. This year, those defensive efforts are being put on display even more. His constant hustle, leadership, and ability to run a defense are what make the Celtics tick on that end of the floor.

Anyone who watches the Celtics has seen Smart make the iconic hustle plays that everyone talks about. They’re the plays that ‘don’t show up on the stat sheet’ and lead to his value being constantly underplayed. He does the dirty work so no one else has to. But just in case you haven’t been watching, here are a few examples.

4. Al Horford as a secondary paint protector

While Williams has been working from the corner, the Celtics have relied on Horford to guard opposing big men. He’s banging down low while Williams gets to come in and reap the reward. However, whenever Williams makes a mistake, is forced out of the corner, or can’t get there in time, Horford has been great at cleaning things up. Horford almost acts like a safety blanket - if Williams isn’t there, Horford is.

At 35 years old, no one expected Horford to be the same player he was during his first stint in Boston. Most people were happy to have him back, and he was always going to have a role, but he’s exceeded all expectations so far this season. He just does all the little things that rarely get noticed on the defensive end.

Obviously, his ability to hang with some of the biggest, most talented centers in the league is what makes Boston’s defense so elite. Without him, Williams would be forced to guard centers, and that would put a damper on Udoka’s entire plan. But it’s been his defensive knowledge of knowing when to help that’s put the cherry on top of the Celtics’ defense. Here are some prime examples.

5. Jayson Tatum and Jaylen Brown’s versatility

Udoka’s switch everything defense only works if everybody on the floor is versatile enough to guard every position. Smart, Horford, and Williams are constantly praised for their defensive abilities, but Tatum and Jaylen Brown are just as impressive on that end of the floor.

While their main focus is, and will always be, getting buckets on the offensive end, they’ve been seriously challenged on the defensive side of the ball this year. Udoka needs them to be fully engaged at all times on that end, and thus far, they’ve done just that. With their amazing length and versatility, Boston has absolutely no weakness on defense.

They’ll switch onto guards, go toe-to-toe with the best wings in the league, and even spend time on opposing centers (although that’s mainly Brown’s job). Both of them are athletic enough, strong enough, quick enough, and smart enough to guard almost anybody in the league. Take a look at these great examples.

6. Individual gameplans

Boston’s general defensive scheme is good enough to stop some of the best offenses in the league, but sometimes there are exceptions. Some teams have players that are so good, the Celtics have to specially prepare for them. In those cases, Udoka has enacted game plans specifically designed to slow that one player down - and they have worked beautifully.

The best three examples of this have been Joel Embiid, Nikola Jokic, and Ja Morant. And remember, the keyword here is ‘slow them down.’ It’s next to impossible to stop guys like Embiid, Jokic, and Morant. The best possible option is to try to slow them down as much as possible.

With Embiid, the plan was simple: either deny him the ball or swarm him once he got it. Embiid is one of, if not the most dominant center in the league. When he gets the ball in the post, there’s very little chance of stopping him in a one-on-one battle. So, the Celtics didn’t let it turn into a one-on-one battle. And on top of that, they forced Embiid to almost exclusively take mid-range shots. They kept him out of the paint at all costs, keeping defenders ready to help on the drive at all times, thus dissuading him from even trying.

Plus, instead of switching everything, they changed their defense so Embiid couldn’t cut to the hoop or get comfortable in the post. They dropped back to deny that look. Embiid ended the game with 19 points while shooting 3-of-9 from the field and 0-of-1 from deep. It was only the second time all season he attempted less than 10 shots in a game.

Next up is Jokic. The Serbian big man does most of his work in the post. Boston’s solution? Don’t let him get to the post, and if he does get there, swarm him or trust Williams. Jokic ended up taking 10 threes against the Celtics (3-of-10), which is nearly six more than he averages. He ended the night with 23 points and 11 assists while shooting 9-of-20 from the field and 3-of-10 from deep. Again, it’s about slowing him down, not stopping him. The Celtics chose to take away his scoring rather than his passing.

That was elite defense; Jokic just made a tough shot.

Finally, the plan for Ja Morant was simple - let him shoot threes. Morant leads the league in points in the paint, so the best way of stopping him was to just not let him get to the paint. In order to do this, the Celtics left Morant wide-open at the three-point line. They dropped back in coverage, allowing him to shoot the three-ball. And it worked.

Morant ended the game with 35 points while shooting 13-29 from the field and 4-of-12 from deep. For reference, Morant only averages 4.5 threes per game. (And the ones he did make all came in the second half. He was 0-for-5 in the first half.) And just as they did with Embiid, the Celtics always had players ready to help if Morant did get the chance to drive.

From Williams to Smart to the rest of the starting crew, there simply isn’t a weak point for opponents to attack. Every single one of them plays their role to perfection.

But as much as the players deserve credit, so does Udoka. He was criticized earlier in the year for his wild defensive approach, but now that the team has had time to master it, he looks like a genius.

As the postseason inches closer, Boston fans should keep one very cliche saying close to their hearts - defense wins championships.