Jayson Tatum scored 31 points and the Boston Celtics held off a furious Dallas rally to reach the brink of a record 18th championship with a 106-99 victory over the Mavericks for a 3-0 lead in the NBA Finals. No team has rallied from 3-0 down in an NBA playoff series. Jaylen Brown had 30 points, eight rebounds and eight assists as the Celtics extended their franchise record with a 10th consecutive playoff victory. The Mavs almost pulled off a crazy comeback to avoid the big hole. Boston led 91-70 at the end of a 20-5 run early in the fourth quarter before Dallas answered with a 22-2 spurt to get within a point.