CLEVELAND, Ohio -- The Boston Celtics are a lot like the Indiana Pacers -- only they have more high-end talent across the board and a better head coach. They are also smarter and more disciplined at both ends of the floor and have shown the ability to win close games that the Pacers couldn't against the Cleveland Cavaliers.

This isn't meant to prompt anyone to mash the panic button.

It's one bad day in a seven-game series, and the Celtics have to duplicate this same effort while perhaps even getting a little bit of luck to take Cleveland's throne atop the Eastern Conference.

Film will be watched. Adjustments will be made. Lineups will change. The final tally doesn't matter going into Game 2. That's the way a series goes.

But the Cavs, much more content with a high-scoring shootout, had better be ready for a fight in the Eastern Conference finals because even without Kyrie Irving and Gordon Hayward, the Celtics will continue to take their swings.

On Sunday, the Cavs didn't look prepared for that. The Celtics copied the Pacers' defensive blueprint, disrupting the Cavaliers' typically explosive offense en route to a 25-point blowout win in the series opener. It was a game in which Cavs coach Tyronn Lue raised the white flag and emptied his bench with about seven minutes remaining in the fourth quarter.

The key to beating the Cavs is -- and has been -- making them as uncomfortable as possible and being incredibly physical, especially on the perimeter.

In Round One, Indiana's feisty style and like-sized personnel disrupted Cleveland's offensive rhythm and pushed the Cavs to the brink of elimination. The Pacers couldn't pull off the upset because they squandered too many chances in crunch time and couldn't overcome the LeBron James Effect.

After enjoying an offensive explosion in the conference semifinals against the Raptors, the Cavs were smothered once again.

Yes, the Cavs missed some shots they normally make. They said after the game they will take those same looks again in Game 2.

But Boston's purposeful defense played a role in those clanks, as it had the Cavs looking indecisive for all but one quarter.

The defensive pressure extended out to the perimeter, with the Celtics using their unique combination of length and athleticism to disrupt entry passes while showing the strength to fight for position in the post.

The Celtics closed out to Cleveland's abundance of outside shooters with a purpose and provided plenty of resistance on dribble penetration. The communication was there throughout, showing why they finished with the league's top defense in the regular season.

"Defensively they're extremely long," JR Smith said. "They got (Jayson) Tatum, he's 6-8, 6-9 with long arms. The same thing with (Jaylen) Brown. Morris is huge -- huge arms, the way he stands. Terry (Rozier) is extremely scrappy. Same as the other guys and it's just tough. We didn't help it by turning the ball over. They put us in tough situations, too, turning the ball over."

The Cavs scored just 83 points, their second lowest total in the postseason.

The were 31-of-86 (36 percent) from the field and 4-of-26 (15.3 percent) from 3-point range.

Their offensive rating: 86.6, which is the first time the Cavs have been below 90 points per 100 possessions since the playoff opener against Indiana.

Boston's defensive plan started with making James see numerous bodies. Stopping him is always out of the question. But making him inefficient is a success.

James, who usually refers to Game 1's as feel-out matchups, had his worst game of the postseason, scoring a playoff-low 15 points on 5-of-16 from the field and 0-of-5 from beyond the arc. James also committed seven turnovers, the most he has had in 12 postseason games.

Many chuckled at Celtics burly forward Marcus Morris for speaking with confidence when asked about his past defense against James. But Morris showed why the Celtics made a starting lineup change and gave him that defensive assignment. He defended the Cavs star on 24 possessions, holding him to just five points on 2-of-6 from the field on those chances and deserves plenty of credit for not backing down.

"I thought they had great game plan Game 1," James said. "He was the start of it. He was my matchup, and I think they did a great job of communicating throughout the whole game, knowing where I was and knowing where our teammates were. Brad (Stevens) and the coaching staff did a great job in Game 1. You commend that.

"We have an opportunity to look at a lot of film tomorrow, and see ways they were making us uncomfortable, making myself off balance and not have a rhythm all game. So we'll be much better in Game 2."

It took Kevin Love 14 shots to get his 17 points. Kyle Korver and Smith, both of whom entered the game shooting better than 40 percent from 3-point range, combined to hit just 1-of-8 from long range. George Hill looked overwhelmed.

Heading into this series, the Cavs felt their seven-game slugfest against Indiana had prepared them for this level of physicality and tenacity. But as Korver said days before heading to Boston, the Celtics are even better than Indiana.

They got an unfriendly reminder of that on Sunday afternoon.