The Celtics are a heavy favorite on Friday night with a spread of -15.5 against the Mavericks. Boston has a moneyline of -1200 while the Mavericks are a +750 underdog. The Celtics are 41-21 overall this season, while the Mavericks are 21-41. Dallas has lost five games in a row, including a 115-114 game to the Magic last night.