BOSTON -- Any chance of a 10-day layoff hurting the Cleveland Cavaliers quickly disappeared Wednesday night.

"Starting the game, LeBron really controlled the tempo, really set the tone early," Cleveland coach Tyronn Lue said after LeBron James scored 15 of his 38 points in the first quarter as the defending champions cruised to a 117-104 victory over the Boston Celtics in the opener of the Eastern Conference finals.

"He's playing at a high level right now, and that's the reason we're riding him so much."

James, looking to advance to his seventh consecutive NBA Finals (the most since Bill Russell in the 1960s) grabbed nine rebounds and seven assists while posting his seventh consecutive 30-point game. He is averaging 34.8 points, 9.0 rebounds and 7.1 assists in the playoffs.

"Amazing, but he's better than when I first got into the league," Celtics fourth-year coach Brad Stevens said.

The Cavs, playing their first game since May 7, put on a clinic, leading wire to wire.

Cleveland built a 26-point lead in the first half, expanding it to 28 -- matching the largest home playoff deficit in Celtics history -- in the third quarter before Boston cut it down to 17 at the end of the quarter. The Celtics rallied some and actually cut their deficit to 11 with the benches cleared in the final minutes.

"I don't even think we played that great tonight," James said. "We definitely didn't shoot the ball as well as we're capable of shooting it. ... I think the energy and the effort and mindset was where it needed to be starting on the road, especially in the Eastern Conference finals."

Kevin Love, who hit four 3-pointers in the third quarter, scored a career playoff-high 32 points and grabbed 12 rebounds, becoming the first Cav other than James to amass 30 points and 10 rebounds in a playoff game since Brad Daugherty in 1992. Tristan Thompson had a career playoff-high 20 points (shooting 7-for-7 from the floor) and nine rebounds, and Kyrie Irving contributed 11 points and six assists.

"Tonight was another one of those games where I made a couple plays to help us get a win, but it was definitely our two bigs (Love and Thompson, who) set the tone," James said. "They were phenomenal."

Lue, a former Celtics assistant, said of Thompson, "He's our energy, he's our motor."

At one point in the third quarter, the Cavs were 28 of 45 from the floor. They finished the game at 48.1 percent.

Game 2 is Friday night at TD Garden before the series shifts to Cleveland for Games 3 and 4.

Avery Bradley and Jae Crowder led the Celtics with 21 points apiece, while Isaiah Thomas, hounded all night, had 17 points and 10 assists. He was just 7 of 19 from the floor, 2 of 7 from 3-point range. Rookie Jaylen Brown had 10 points and nine rebounds off the bench.

Thomas hit a 3-pointer with 2.8 seconds left in the first half, his team's second trey in 16 first-half attempts.

Asked if the Celtics had a bit of a letdown after an emotional seven-game series with the Washington Wizards, Thomas said, "I don't think so. They were the better team tonight. They hit us first. They were more physical ... on both ends of the floor, and that was the difference."

"I think their energy level was by far higher than ours to start the game," Crowder added.

The win was the Cavaliers' 12th in a row in the playoffs (one shy of matching the NBA record, set by the 1988-89 Los Angeles Lakers), dating back to last year's finals, while the Celtics' five-game home playoff winning streak was stopped.

Some third-quarter unpleasantness erupted between Thompson and Boston's Marcus Smart, whose fiery play kept his team somewhat alive -- his flying slam on a rebound with 2.8 seconds left in the third igniting the crowd. The pair were whistled for double fouls on one occasion and came together on other occasions.

Before the season, the basketball world was predicting a Cavaliers-Golden State Warriors rematch in the finals. The teams are a combined 19-0 in this postseason, the first time two teams ever started one playoff year 9-0.

NOTES: Cleveland F LeBron James reportedly erased a white board of plays when told Boston F Kelly Olynyk had 26 points in Game 7 against Washington on Monday night. "Seriously?" he said. "We had like two weeks to get ready and now at the last second it turns out Kelly Olynyk has the ability to make shots and get rebounds and stuff? Well, back to the drawing board I guess." Olynyk scored two points in the final minute and had three rebounds Wednesday. ... Boston C Al Horford on the Celtics getting the top pick in the lottery: "That's big for our franchise. The first time in history -- that's pretty cool." ... Celtics coach Brad Stevens on winning the lottery: "It's a great opportunity for us." ... Former Red Sox DH David Ortiz was seated next to the Celtics' bench.