The Boston Celtics wear opponents down with defense. It is difficult to generate a clean look against them in the halfcourt, since they hardly play anybody who can be called a weak link. Their bigs are nimble and athletic, and their perimeter players are long and strong. Boston's game plan, broadly speaking, is always about keeping its opponents out of their comfort zone. Over the course of a game, over the course of a series, the energy that opponents have to expand on offense adds up.  

"I think the mental stress and strain we put on some teams with our defense has worked and carried us through the playoffs at times," Celtics coach Ime Udoka said after a grimy Game 5 win in the conference finals. "You saw in the Brooklyn series, guys started to wear down. Game 7 [of the second round], it looked like [Giannis] Antetokounmpo slowed down some. But just having all those bodies to continue to throw at people wears down on them physically and mentally."

The Golden State Warriors wear opponents down with offense. They don't stop moving, and they don't let you relax. Every second that you are defending Golden State, you are one tiny mistake away from surrendering an open 3-pointer to Stephen Curry or Klay Thompson. That is enormously stressful, and coach Steve Kerr's system Is designed to exploit that stress. Make one tiny mistake in the name of slowing down a Splash Brother, and another Warrior has a layup. 

"We have a game or style of play that kind of wears people out," Golden State big man Kevon Looney said Monday. "The first half, everybody's locked in, the defense is locked in onto the game plan. But we got guys like Steph and Klay and Jordan [Poole] that don't stop moving and Draymond [Green], who's gonna push the pace the whole game. And by the time the third quarter comes, we get our early turnovers out that we usually get and we kind of settle in and lock in and the ball starts moving around and the crowd gets behind us and Steph turns into another person in the third.

"We've been doing it for years," he continued. "I think it's just our style of play. I don't know if Steph gets the credit for being one of the best in-shape athletes in the NBA. He runs around the whole court, I think he kind of starts to break defenders' will in that third quarter with his movement and our passing."

When these two teams meet in the NBA Finals, starting Thursday, you will see all the standard strategic battles -- every matchup, coverage and rotation decision will reveal something about each team's plan of attack. Underneath all that, though, both teams will be trying to win the war by depleting the opponent's energy. 

Boston's philosophy: Nothing easy

Everything the Celtics do defensively starts with their ability to hold up one-on-one. They switched ball screens more often than any other team this season, baiting opponents into isolation basketball and contested, late-clock shots. Everybody in the playoff rotation -- even Payton Pritchard, who is often targeted because he's small -- plays physical perimeter defense, and Udoka trusts everybody to stay in front of the ball. 

After the Celtics went up 3-0 in the first round, Brooklyn Nets big man Blake Griffin shook his head at the podium as he described what makes them great defensively: They "shrink the floor and then also get out to everybody else." Boston is full of long, active help defenders who can eliminate driving lanes, jump into passing lanes and still close out on shooters. Marcus Smart won Defensive Player of the Year as much for his off-ball playmaking and communication as for what he does at the point of attack. Robert Williams III is always roaming, lurking and erasing would-be advantages. 

In their first-round sweep, the Celtics did not allow Kevin Durant or Kyrie Irving to play in space or catch a rhythm. They held them to 1-for-17 shooting in the second half of Game 2, and, the next game, forced Brooklyn to play Durant and Griffin next to three small guards. This helped the Nets' spacing, but ultimately doomed them defensively. 

The Celtics lost the opener against the Milwaukee Bucks, but found their formula in Game 2: Limit transition points, limit second-chance points, empower Grant Williams and Al Horford to defend Giannis Antetokounmpo one-on-one and stay home on shooters. It was not exactly smooth sailing for Boston from there -- a fourth-quarter rally fell short in Game 3, and it stumbled down the stretch of Game 5 -- but it controlled Game 6 and suffocated the Bucks' offense in Game 7.  

The Celtics changed their pick-and-roll coverage and their matchups as the conference finals progressed, but that formula stayed the same: As long as they didn't give up easy run-outs, they could grind Miami's offense into the mud. The Heat's best game was the opener, and, when Boston led 98-85 with 3:35 remaining in Game 7, it looked like it was going to finish the series as comfortably as it did the previous one.

What do we make of what happened next? Uh, let's come back to that. 

Golden State's philosophy: Decisions, decisions, decisions

The Warriors' offense revolves around Curry, who on Monday referred to his mix of on- and off-ball skills as his "superpower." It was built, however, on Kerr's fundamental belief: for a team to be more than the sum of its parts, every player must be a threat at all times. 

The Platonic ideal of a Golden State possession starts with a purposeful action that targets a weakness -- say, a pindown screen involving a subpar defender -- and continues with a series of improvisations. The Warriors have set plays, but they mostly play out of concepts, which allows them, at their best, to find a flow that makes everything look effortless. Defending this is exhausting.   

"The main goal," Curry told ESPN in 2017, "is to just make the defense make as many decisions as you can so that they're going to mess up at some point with all that ball movement and body movement and whatnot."

In its first two games of the playoffs, Golden State trailed by one point at the end of the first quarter and led by 22 late in the third. The Nuggets adjusted by sacrificing offense for defense, cutting Bryn Forbes' minutes in Game 4, their lone win, and playing Aaron Gordon 40 minutes in Game 5. The Warriors trailed that last game after three quarters, then went on a series-ending run. 

Against the Memphis Grizzlies, Golden State fell down by double digits in the first quarter of Game 1 and went down 8-1 and 9-2 in the next two games. The Warriors won 142-112 -- not a typo -- in Game 3, then, playing against a Memphis team missing Ja Morant, erased a 12-point fourth quarter deficit to win Game 4. They didn't win a first quarter until Game 6, and then they sent the Grizzlies home with a 21-3 run in the fourth. 

In Game 2 against the Dallas Mavericks, the Warriors went on a 30-10 run in the second half to win a game in which their opponent made 21 3s. They started slow in Game 3, then went on a 10-0 run to take the lead before halftime and extended it to double-digits in the third. Dallas dominated Game 4 until Golden State's reserves went on a 32-11 run in the fourth quarter, making both coaches put starters back in. When the Warriors built a 25-point lead in Game 5, the Mavs were finished. 

Something has to give

In the regular season, the Celtics (+11.8) and Warriors (+10.5) were the two best third-quarter teams in the league, on the basis of per-possession point differential. They were both elite in the fourth, too, if you only look at Boston's numbers after its collapse at Madison Square Garden on Jan. 6, the game that Tatum called the low point of their season. The Celtics weren't a particularly poised team early on, but for about five months they've made the case that those issues are behind them, most convincingly in the final two games of the Bucks series. 

The last thing we saw Boston do, however, was almost blow an 13-point lead in the closing minutes of Game 7. With an NBA Finals berth on the line, the Heat went on an 11-0 run and Jimmy Butler missed a transition 3 that would have given Miami the lead. This comeback would not have been possible without the Celtics rushing their offense, turning the ball over and mismanaging the clock. 

In defense of the Celtics, Miami needed Kyle Lowry to make a tough 2 over Tatum and Max Strus to come up with a putback dunk and a crazy 3. It's not as if the Heat had somehow solved Boston's defense, which held them to 75.9 points per 100 halfcourt plays in Game 7. In a sense, the final few minutes did reinforce something positive: The Celtics' defense is stifling enough to get them across the finish line, as long as they don't sabotage their title chances with bad decision-making and live-ball turnovers.  

The Finals' most important questions are about what happens when Golden State has the ball. Can the Warriors look like the Warriors against a defense this strong? Can Boston lock in and disrupt an opponent that is this committed to ball movement and body movement, led by a multi-time MVP that is dangerous from everywhere, with or without the ball? Neither side has seen a challenge like this in these playoffs. 

Curry is used to the bump-grab-and-hold treatment, but it's more annoying when Smart is the one doing it (and then drawing fouls on push-offs and illegal screens). If Smart is on Curry and Tatum is on Green, then the Celtics can simply switch the Curry-Green pick-and-roll. Derrick White essentially erased Strus' off-ball stuff in the conference finals, and he'll surely get a chance to chase Curry around screens. 

"What they do well is shoot the ball, but I think teams can kind of overdose on that at times and it's a lot of the little things that get them going," Udoka said Tuesday. "Basket cuts, slips to the basket. You're so concerned about their 3-point shooting that they get a lot of other things."

Is Smart healthy enough to hold up as Curry's primary defender for a whole series? Is Robert Williams III healthy enough to roam and recover the way he normally does? Is this going to be the first time that Horford and Grant Williams, so stellar throughout the playoffs, are not quite mobile enough on the perimeter? Is this going to be the first time that Green and Looney can't quite make up for their lack of shooting with skill and savvy? Just how much switching is Boston going to do? 

Curry played only 14 minutes in the Celtics' 110-88 win in San Francisco in March. When he left with a foot injury, though, there were about four minutes left in the first half and Golden State had scored only 25 points. 

"I think that game was a really good indicator of how good Boston is defensively," Kerr said Tuesday. "And that was kind of right at the height of their rebound after the new year where they kicked it into gear and started playing fantastic defense. We felt it that night."

It's all connected

One cannot, however, cleanly separate all of the above from what happens on the other side of the court. If Golden State needs Poole's playmaking, then it needs him to survive when Boston goes at him on the other end. If it needs Nemanja Bjelica's shooting, same thing. The Celtics had no issues against zone in the conference finals, but Miami used it mainly to cover up for poor individual defenders, while Golden State will use to challenge iffy shooters and make Boston think. Regardless of the coverage, if the Warriors, who forced more turnovers than all but one team in the regular season, can speed up the Celtics, get stops and get out in transition, then they won't necessarily need all the pretty stuff to work in the halfcourt. They'll be better equipped to do that if Gary Payton II and Andre Iguodala are available. 

Turnovers are Golden State's Achilles' heel, too, and they have driven Kerr crazy since the day he arrived. "We've won championships being a high-turnover team, but it can't be obscene," he said during the Memphis series. To an extent, it is an acceptable by-product of playing with the pass, playing with pace and playing with aggression, but when the Warriors sloppily sling the ball around, they are playing with fire.

Heading into the Finals, both Boston and Golden State will emphasize the importance of making the simple play, winning the possession game and preventing fast breaks. Both teams, know, however, that tired teams tend to turn the ball over. They want to tire each other out and win the long game. Whatever happens in Game 1 on Thursday, try not to read too much into it.