Kirk Goldsberry wrote:How the Boston Celtics vaulted back into championship contention with the NBA's best defenseWhile the eyes of the basketball world were focused on the off-court moves of the Philadelphia 76ers and Brooklyn Nets, who swapped disgruntled superstars at the trade deadline last month, it was another Atlantic Division team that was making significant moves off the court.
Although you wouldn't know it from their dud against the Indiana Pacers on Sunday, the Boston Celtics are the hottest team in the Eastern Conference and looking like the contenders many pegged them to be at the start of the season. The Celtics are 17-6 in their past 23 games and have climbed out of the play-in spots in the standings.
First-year coach Ime Udoka has turned around a squad that was 18-21 and in 11th place in the East on Jan. 7, forging them into a legitimate threat to reach the NBA Finals. How have the Celtics done it? One word: defense.
Since hitting their low point in early January, the Celtics have a defensive efficiency of 101.5 -- and that's after giving up 128 points to the Pacers on Sunday. The Miami Heat have the league's second-best defense in that span, allowing 107.1 points per 100 possessions. To put in perspective how much better Boston has been than the rest of the league, that difference of 5.6 points is roughly the same as the difference between the second-place Heat and the 18th-place Utah Jazz.
The 2021-22 Celtics are playing less like the '86 Celtics and more like the '85 Chicago Bears. This defense has been off the charts in a good way.
Udoka and the Celtics coaches have aligned their defensive talent with a few signature schemes, and the results this calendar year have been so great that it's fair to consider this team a real threat to come out of the East.
In a league obsessed with pick-and-roll actions, the best defenses are capable of stifling those bread-and-butter plays at the point of attack. Boston's big, versatile defenders are perfect for that task in part because they have size and physicality, but also because they communicate well on the floor.
The Celtics roster is chock-full of impressive defenders. They have longtime Celtics Marcus Smart (a two-time All-Defensive Team selection) and Al Horford (who earned All-Defense honors in 2018), they brought back solid big man Daniel Theis and they added Derrick White, who proved himself a strong defender in San Antonio, at the deadline. But what's happened in January and February is that a roster full of solid defenders has effectively coalesced into something much greater than the sum of its parts.
Boston has been the best team at defending on-ball screens during the calendar year, allowing just 0.87 points per play on direct on-ball screens, according to Second Spectrum. This impressive mark is largely due to this team's outstanding ability to switch assignments at a high volume without ending up with mismatches.
Since Jan. 1, the Celtics have switched 673 times vs on-ball screens -- the second-most in the NBA during that span, behind only the Heat. Boston has given up only 0.83 points per direct play when switching in 2022, the best such mark in the NBA.
Consider this basic question: Which team has the least efficient offense in the NBA in 2022?
It's not the Oklahoma City Thunder. The Thunder have scored just 103 points per 100 since Jan. 1, which ranks 30th in the league. It's whichever team is playing Boston.
Celtics opponents are managing just 100.9 points per 100 possessions in 2022. This Celtics defense turns whoever they are facing into a dumpster fire that can't even score as efficiently as a tanking team logging the worst offensive markers in the NBA.
Udoka has settled in on a starting group that pairs superstar wings Jayson Tatum and Jaylen Brown with Horford and Smart along with fourth-year center Robert Williams III. Few people thought the 35 year-old Horford had much left in the tank, but he's played more than 1,500 minutes -- fourth most on the team -- and provided Boston with the exact kind of veteran leadership that it has lacked in its front court since he departed in 2019.
Horford's return and Udoka's arrival also set the stage for the emergence of Williams, who provides the Celts with one of the most springy, most versatile defensive bigs in the league. He's the exact kind of anchor in the middle who enables a team to switch as much as the Celtics do, and his ability to disrupt shots is already world-class. Williams has held opponents to 37.8% shooting as the closest defender. That is the lowest in the NBA this season and the second-lowest over the past five seasons by any of the 847 players who defended at least 500 shots.
He ranks third in the league in blocks and 14th in rebounding despite playing fewer than 30 minutes per game. He's a key reason for this Celtic reawakening.
The combination of the veteran wisdom of Horford and the youthful explosiveness of Williams make this frontcourt one of the best such units in the league, but the two players are by no means alone.
Tatum, Brown and Smart are all long, strong, and willing stoppers too. There's no one small or light. There are no lazy defenders to hunt. The perimeter defense is elite too, and the deadline addition of White only makes Boston better.
ESPN's NBA Basketball Power Index
Who is No. 1 in the latest NBA Basketball Power Index? Go to Ratings
It's easy to be fooled by the standings, which show Boston at No. 6 in the East, just two games clear of play-in territory. But the underlying numbers leave little doubt that this team is for real, and needs to be taken seriously as a threat to win the Eastern Conference in the postseason. Even with that disappointing start factored in, Boston is outscoring teams by 5.3 points per game, the largest margin among East teams.
The Celtics are 19-6 when their preferred five-man lineup starts -- Horford sat out Sunday's loss as part of a plan to manage his minutes after he'd played 37 the night before -- and among the 24 NBA lineups that have logged at least 200 minutes together this season, Boston's starting five ranks first in net rating, seventh in offensive efficiency, and first in defensive efficiency.
In their 322 minutes together on the floor, the Celts' starters are outscoring opponents by 26.6 points per 100 possessions. Folks, that is ludicrous. No other five-man group with at least 200 minutes together is even close to that. The defending champion Milwaukee Bucks' best five-man group (Giannis Antetokounmpo, Khris Middleton, Jrue Holiday, Bobby Portis and Grayson Allen) is at plus-13.2. The Golden State Warriors' best five-man lineup features three All-Stars (Stephen Curry, Draymond Green, Andrew Wiggins), and they're a plus-8.2, not even one-third as good as what the Celtics' starters have done.
FiveThirtyEight's RAPTOR projection model gives Boston a 30% chance of reaching the Finals (better than any other Eastern Conference team) and a league-best 18% chance of raising the franchise's 18th NBA championship banner.
While the numbers are screaming at us to pay attention to Boston, so is recent history. Tatum and Brown are just entering their primes, and Boston has already made appearances in three of the past five Eastern Conference finals (the first of which came before Tatum was even on the team). This team has the star power to make it four of six, and, after an uneven start to this season, appears to be peaking at just the right time.
https://www.espn.com/nba/insider/insider/story/_/id/33348162/how-boston-celtics-vaulted-back-championship-contention-nba-best-defense 
