Cleveland Cavaliers' LeBron James (L) shoots over Boston Celtics' Tony Allen during the first quarter in Game 5 of their NBA Eastern Conference playoff basketball series in Cleveland, May 11, 2010. [Xinhua/Reuters Photo]

Ray Allen scored 25 points and Rajon Rondo scored all of his 16 in the second half as the Boston Celtics beat the Cleveland Cavaliers 120-88 in Game 5 on Tuesday to move within a win of knocking the NBA's top team from the playoffs.

Paul Pierce added 21 and Kevin Garnett 18 for the Celtics, who handed the Cavs their worst home playoff loss in history and can end Cleveland's season with a win in Game 6 on Thursday night.

LeBron James, the league's two-time most valuable player on the verge of an expected trip into free agency on July 1, was underperforming. He scored 15 points on 3-of-14 shooting.