Even after the move, the Celtics still need to trim nearly $20 million to get under the second luxury tax apron and another $20 million beyond that to escape the luxury tax entirely. Because of that, league sources believe the Holiday trade will be only the first domino to fall for Boston. The Celtics are still shopping other players, including Kristaps Porziņģis, with an eye on alleviating their salary-cap dilemma, according to league sources.