The Cleveland Cavaliersí playoff run reached an inflection point Tuesday in a 107-94 loss to the Boston Celtics, and frustration appeared to take over on an ugly foul committed late in the game by guard J.R. Smith. The Cavs, in the midst of a 39-point second half while blowing a seven-point halftime lead, were running out of time against a Celtics team that had wrested control of the game with a chance to take a 2-0 series lead. With just under four minutes to play, Boston forced a Cavs defensive switch that left Al Horford with a clear path to the basket and a lob pass from Marcus Smart.