BOSTON -- For the second time in the three postseason series the Cavaliers have played this spring, LeBron James & Co. find themselves needing to bounce back from a blowout loss in Game 1, after the Celtics trounced Cleveland 108-83 on Sunday.

"We didn't play well," Cavs coach Tyronn Lue said matter-of-factly. "We understand that. We know we have to be better."

The Cavs were outscored 36-18 in the first quarter and trailed by as many as 29 points. Cleveland's 26-point halftime deficit was the largest in James' 229-game postseason career. The Celtics outscored the Cavs 60-38 in the paint and had a 48-40 edge in rebounds.

"Bad game," Kyle Korver said. "Bad first game. There's lot of things we can do better in the next one."

Tristan Thompson was more direct in his critique.

"They punked us," he told ESPN. "Early and often."

James saw his six-game playoff winning streak in Boston snapped and turned in his worst game of the postseason, with 15 points on 5-for-16 shooting, seven turnovers and a plus-minus of minus-32 offsetting his nine assists and seven rebounds.

Still, he showed patience with his assessment.

"I have zero level of concern at this stage," James said. "I didn't go to college, so it's not March Madness. You know, you get better throughout the series. You see ways you can get better throughout the series. But I've been down 0-1, I've been down 0-2, I've been down before in the postseason. But for me, there's never no level of concern, no matter how bad I played tonight with seven turnovers, how inefficient I was shooting the ball.

"I'm just as confident going into a series whether it's a 0-0 series or I'm down 0-1. So we have another opportunity to be better as a ballclub coming in Tuesday night, and we'll see what happens."

Perhaps fueling James' confidence, besides all his experience, is the rationalization that it would be difficult for the Cavs to play much worse.

Cleveland missed its first 14 3-point attempts and finished the game 4-for-26 from the outside (15.4 percent). The Cavs came into Sunday making an average of 10.8 3-pointers per game on 35.1 percent shooting this postseason.

"I mean, 3-point shot is a part of our DNA," James said. "It's what makes us the best team that we can be. I think even early on with the shots that we had, we had some wide-open looks that just didn't go."

Indeed, the Cavaliers shot 1-for-12 on uncontested 3-pointers in Game 1 (8.3 percent) after shooting 45 percent on open 3-pointers this postseason coming into the Eastern Conference finals, according to ESPN Stats & Information.

"We're going to take those same looks going into Game 2 if the opportunity presents itself," James said. "The 3-point shot has been a big part since we pretty much assembled this team four years ago, and I think it's going to be a big part of it throughout the series, as long as we continue to get the ball moving and guys feel in good rhythm."

Still, not all the Cavs agreed with James' continued trust in the long ball.

"We have to put the ball on the floor or something," JR Smith, who was 0-for-3 from deep, told ESPN. "We're living and dying with the 3."

Thompson also brought up the losses of players such as Channing Frye and Richard Jefferson (not to mention Kyrie Irving) since Cleveland's last postseason run a year ago as evidence that the Cavs might not have the outside firepower they used to.

Kevin Love (17 points, 8 rebounds, 3 assists) led the Cavs in scoring, yet the rhythm Cleveland had shown with him and James on the court together in the playoffs went missing Sunday. The Cavs had an offensive efficiency of 86.8 points per 100 possessions with James and Love on the floor, according to ESPN Stats & Information, a stark difference to the offensive efficiency of 113.1 points per 100 possessions that the duo generated the rest of the playoffs.

"We know we just have to come in the next game and play better," Love said. "On both ends of the floor, we didn't play so great. ... They're a very good team. They've played extremely well throughout these playoffs. A number of guys have stepped up for them and played extremely efficient basketball. We're not pressing the panic button. We're going to go back to the drawing board and find what we can get better on the defensive end and let the offense take care of itself."

Lue also called out the Cavs backcourt, saying, "Our guards let down on defense, and we can't do that." The Celtics ended up shooting 51.2 percent from the floor as a team.

"On the defensive end, we weren't very sharp," Korver said. "We weren't as aggressive as we should've been. A lot of it was because we were frustrated on the offensive end."

In the first round, the Cavs dropped Game 1 98-80 to the Indiana Pacers and rallied to win the series in seven games.

"I thought it was similar to Game 1 against the Pacers," Korver said. "We came out and lost by 18 at home. It was a tough loss. But this team's been around this before. We'll watch the film and try to get better."

With the blowout in the books, James looked ahead to Cleveland's next shot to even things up.

"Game 1 has always been a feel-out game for me, if you've ever followed my history," he said. "So I've got a good sense of the way they played me and how I'll play going into Game 2."