The Celtics seized the lead in the best-of-seven Eastern Conference finals, with the winner to face either season wins leader Houston or defending champion Golden State in the NBA Finals. The Celtics, who host game two on Tuesday, jumped ahead 36-18 after the first quarter and never looked back, the Cavaliers coming no closer than 14 points in the second half. "We were great," Horford said. "We came out with a lot of energy. We fed off the crowd and we kept it going throughout the game. We're just out here playing hard and doing the best we can." Marcus Morris had 18 points and 11 rebounds for Boston and Jayson Tatum added 16 while Brown had eight rebounds and Terry Rozier contributed eight points and seven assists. James averaged 34 points, 9.4 rebounds and 9.0 assists in the first two rounds of the playoffs but the superstar playmaker, seeking an eighth consecutive NBA Finals berth, was shut down by an aggressive, hustling Celtics squad. "We just have to make it hard for him," Celtics coach Brad Stevens said of James. "Our guys played with good aggression. They will have to do that again Tuesday." James finished with 15 points on 5-of-16 shooting with seven rebounds and nine assists. He blocked two shots but also made seven turnovers. "They showed two bodies (guarding James) all night," Cavaliers coach Tyronn Lue said. "When he thought he had driving lanes, they made him kick it out to other shooters." The Celtics forced James to work harder defensively and rotated several players on the four-time NBA Most Valuable Player to contain him offensively. "We lost," Lue said. "We didn't play well. We know we have to play better. They attacked us early on. We had some great shots we couldn't make and it snowballed from there." Talented 20-something players Tatum, Rozier and Brown have filled the void left by injured stars Kyrie Irving and Gordon Hayward, combining with Horford -- who has been eliminated by James four times in the playoffs -- to become a formidable force that out-hustled the more experienced Cavaliers and dominated defensively. "They are just embracing this opportunity," Horford said. "We have a great opportunity in front of us and we're enjoying it game by game. I try to lead them the best way I can, lead by example." Morris, who boasted he was the best defender to guard James, started and contained the Cleveland superstar, who has more career playoff appearances than the entire Celtics roster combined. "He's a tough player," Horford said. "He knows how to defend. He has a great feel for that."                  

- Celtics dominate early -                  

Kevin Love led Cleveland with 17 points and eight rebounds. Tristan Thompson had a game-high 11 rebounds off the Cavs' bench.Boston seized a 63-35 lead early in the second half but the Cavs halved their deficit, Jeff Green's jumper at the third-quarter buzzer pulling Cleveland within 78-64 entering the fourth. Boston answered with a 7-0 run to start the fourth. A Morris dunk, Marcus Smart 3-pointer and Tatum layup stretched the Celtics' lead to 85-64 as part of an 18-4 run that would put Boston ahead 96-68 and end Cleveland's hopes. Boston surged ahead 61-35 at half-time, paced by Brown's 18 points and seven rebounds and Horford's 14 points and five assists.James shot only 3-for-8 in the first half and the Cavaliers missed their first 14 3-point attempts of the game.  The Celtics opened an early 29-9 lead and a 25-2 run helped carry Boston to a 36-18 edge after the first quarter.Brown scored 13 points in the first quarter while Horford added 11 and the Celtics owned a 14-6 rebounding edge.