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Six days before the Boston Celtics won Game 7 of the Eastern Conference finals on the road, they desperately needed to win Game 4 at home. They were down 2-1 in the series, and they were coming off a disheartening loss in which Miami Heat star Jimmy Butler played zero second-half minutes. 

During coach Ime Udoka's pre-game press conference last Monday, a reporter asked about an unusual stat that had turned into a talking point: The Celtics had only outright lost two quarters in three games. Udoka said that the important thing was not how many 12-minute periods they had lost, exactly, but "being consistent and not falling off a cliff the way we did in those two quarters when our offense is not flowing." Boston had allowed 39 points in the third quarter in the opener, and it had given up the exact same number in the first quarter of Game 3.

"More so than anything, we like to keep teams in the mid-to-low-20s per quarter," Udoka said.

The mid-to-low-20s. That, in the NBA of 2022, is an absurd goal. This is a league in which the Oklahoma City Thunder, its worst offensive team, averaged 103.7 points per game, i.e. about 26 points per quarter.

For the Celtics, though, it has proven reasonable. In their four wins against Miami, their defense allowed 26 or fewer points in 13 of 16 quarters. One of the other three came in Sunday's 100-96 clincher -- the Heat scored 32 points in the second quarter of Game 7, thanks to Butler's brilliance and Boston sending them to the free throw line over and over again. The other two were fourth quarters of blowout wins. 

Out of the 28 quarters that comprised the series, Miami managed more than 26 points only nine times, including those two garbage-time-heavy periods. The Heat are an elite defensive team, too, and they had a chance to overcome this, right down to the final minute, but their offense -- above average in the regular season -- far too often turned Thunderesque.

"We just couldn't get control of the game," Miami coach Erik Spoelstra said. "A lot of that was Boston. We didn't stop grinding and we gave ourselves a shot at it at the end. We just couldn't make enough plays during the course of the game. It felt like most of the game we were grinding from an eight- to 10-point deficit."

This is what Boston's defense does. In the second round against the Milwaukee Bucks, it was just as stifling: Another seven-game series, another 19 quarters in which the Celtics allowed 26 or fewer points, another four wins in which the opponent cleared that number only three times. The Bucks scored 99.4 points per 100 halfcourt plays in the regular season, which ranked sixth in the league, per Cleaning The Glass, and scored just a horrific 81.9 per 100 in the halfcourt against Boston. (As a point of reference, Oklahoma City and the Detroit Pistons ended the season in a last-place tie: 88.6 per 100.)

In the Heat's four losses in the conference finals, they scored 85.2, 65.7, 58.8 and 75.9 points per 100 halfcourt plays, respectively. Just before tipoff on Sunday, ESPN aired footage of Udoka in the locker room telling the Celtics not to let Miami get easy buckets early on, to be disciplined, to take care of the ball and to protect the defensive glass. Throughout the playoffs, when Boston has avoided the silly stuff and forced its opponent to try to score against a set defense, it has always thrived, home or away.

In Game 7, the Celtics "hit all the targets that we wanted to," Udoka said. They finished with 13 turnovers, and only three of those led to a Heat transition opportunity. They won the rebounding battle and surrendered only nine second-chance points. Miami shot 6 for 30 from 3-point range. After cutting Boston's lead to three with about 11 minutes to play, the Heat missed nine straight shots, going scoreless for more than four minutes. 

"Defense is our identity," Udoka said. "It's been there and held us, got us through the tough times when the offense wasn't clicking. Games when the offense doesn't click to the level it should, we can always rely on that. And that was the case tonight. We got big leads, dwindled it down and we continued to get stops when we needed to."

On one picture-perfect defensive possession in that stretch, Miami's Kyle Lowry spent most of the 24-second shot clock probing for an advantage, eventually giving Victor Oladipo a chance to attack the basket on a dribble-handoff. When Oladipo took off, though, Al Horford was right there with him. Oladipo tried a reverse layup, but Horford blocked it with his left hand and secured the rebound immediately:

Miami got a stop after that, and then it looked for early offense. Bam Adebayo handed it off to Butler, but with Jaylen Brown going under the screen and Horford in a drop, Butler decided not to attack right away. Adebayo set another screen, Butler rejected it and Brown stuck with him on his drive, then stayed down on his pump fakes. This forced Butler into a desperate, heavily contested jumper:

A few minutes later, the Heat ran a sideline out-of-bounds play for Max Strus. It worked, I guess, in the sense that it was able to generate a 3-pointer. But look at Tatum switch onto him, stay attached and contest the shot, and then look at how far Strus is from the basket when he gets into his shot -- this is a deep, difficult, uncomfortable look: 

Horford spoke proudly post-game about the Celtics chasing shooters around the perimeter. He said it's hard to guard Strus and called Lowry "very shifty." When Miami's offense is at its best, it attacks you with a mix of mismatch-hunting, transition play, movement and shooting. For much of Game 7, it felt like the only thing that was working for the Heat was Butler's hero ball. If Butler couldn't create anything, a possession might end with, say, Derrick White switching onto Lowry and forcing a horrendous turnaround 3: 

In a series this tight, the Heat will surely wonder if the playmaking and shooting of Tyler Herro, who played only seven minutes in Game 7 and missed the three preceding games because of a groin injury, could have made a difference. Boston would have picked on him on the other end, though, because it does not believe in letting poor individual defenders off the hook. If a good offensive player hurts your defense, thereby helping the Celtics set their defense, then how much is that player really helping your offense? These are the kind of insane questions that Boston forces opposing teams to consider.   

Throughout the playoffs, it has been the same story for the Celtics: They are terrifying defensively, and, while they've had some setbacks, slip-ups and sloppy stretches, they tend to find themselves before it's too late. This was true in each game of the first round against the Brooklyn Nets -- one of the closest sweeps in NBA history -- and it has been true in both subsequent series. 

"It's hard to win in this league, especially in the playoffs," Brown said. "Any given night, things could go differently, but a good team is able to respond. A good team is able to put their best foot forward each and every night. There was a couple games we felt got away from us, and instead of carrying it like baggage we wore it like a badge of experience to help us get prepared for the next game."

To Brown, Game 7 was "the biggest test, not just of the year, but of our careers." And now that they've passed it, their reward is an even bigger one. For months, the Celtics have been the most balanced team in the NBA, and, against Miami, they showed that they're more than happy to win games in the mud. The Golden State Warriors are pretty balanced themselves, though, and the trio of Stephen Curry, Draymond Green and Klay Thompson has scrambled superb defenses before. The Heat have skilled improvisers in Butler and Lowry, and they are sort of Warriors-like in the way that they try to free up their shooters and pass out of the post, but no one does Golden State things with the speed, shooting and sheer conviction of Golden State.    

In the Finals, that mid-to-low-20s goal might actually be absurd, even for Boston. The way the Celtics see it, though, they should be stronger than ever, precisely because of what they just survived. 

"Very confident going in," Udoka said. "I know it's another tough challenge. It think Miami will help prep us for some of the off-ball actions and the shooters that they have. But we know it's a high-level team, executing team, that has a ton of great shooters, great players overall, guys I know well. And we're ready for the challenge."