The Spurs won their fourth straight road game and their seventh straight against the Grizzlies. San Antonio was playing its first game without center Tiago Splitter, who sprained his right shoulder in Saturday's win over the Clippers and is out for three to five weeks.
Memphis never led in the game until Conley connected on a 3-pointer with 2:25 to go in overtime for a 103-102 advantage. The Grizzlies also led 106-104 after newly acquired guard Courtney Lee hit a jumper with 1:27 to go, but Boris Diaw scored on a layup 25 seconds later and Duncan hit two free throws with 22.6 seconds left for a 108-106 lead.
The Grizzlies dropped to 0-9 against Southwest Division opponents.
The Spurs shot 57 percent in the first half and built a 53-41 lead. San Antonio was 23-of-40 shooting and Belinelli had 14 points. Duncan was 5 of 7 and scored 11 points.
The Spurs led by as many as 14 in the opening half.
Leading 25-22 at the end of the first quarter, the Spurs extended their advantage to 14 at 47-33 late in the second quarter and maintained a double-digit lead until the second half.
In the third quarter, the Grizzlies trimmed San Antonio's lead to 62-57 on a jumper by Conley, but the Spurs led by 10 entering the final quarter.
NOTES: Grizzlies guard Tony Allen missed his second straight game with a left hand contusion. ... The Grizzlies recalled guard Jamaal Franklin from the NBA Development League's Fort Wayne Mad Ants Tuesday. Franklin, the franchise's second-round draft pick a year ago, played one game for Fort Wayne and scored 15 points with four steals in 23 minutes. ... Lee, acquired from the Celtics as part of a three-team deal, made his debut and connected on his first shot, a 3-pointer in the second quarter. . . . San Antonio improved to a league-best 14-3 on the road this season. . . . The Grizzlies had won a franchise-record six straight overtime games before Tuesday night's loss.