BOSTON — Roger Mason pulled up and leaned into a 3-pointer with 20.4 seconds left, and Tim Duncan scored 23 points with 13 rebounds Sunday to lead the San Antonio Spurs to a 105-99 victory over the Boston Celtics.

It was the second loss in three games for the defending champions, who lost to the Los Angeles Lakers on Thursday in an NBA finals rematch to snap a 12-game win streak.

Kevin Garnett scored 26 points with 12 rebounds, Paul Pierce had 19 and eight and Rajon Rondo had 16 assists for the Celtics.